Hexadecimal digits represented 0 to 9 and A to:

The correct answer is B, Ctrl + 3. Pressing Ctrl + 3 turns the contents of the selected cell or range italic in Microsoft Excel, and pressing it again removes the italics; Ctrl + I does exactly the same job. Excel keeps a whole set of number-key shortcuts for formatting, which is worth learning as a block: Ctrl + 1 opens the Format Cells dialog box, Ctrl + 2 applies or removes bold, Ctrl + 4 underlines, Ctrl + 5 strikes a line through the text, Ctrl + 8 shows or hides outline symbols and Ctrl + 9 hides the selected rows. Option A is wrong because Ctrl + 4 applies underline, not italics. Option D is wrong because Ctrl + 2 applies bold. Option C is wrong because Ctrl + 6 switches the display of objects on the sheet on and off. Exam tip: in Excel remember the run Ctrl + 1 Format Cells, Ctrl + 2 bold, Ctrl + 3 italic, Ctrl + 4 underline and Ctrl + 5 strikethrough.

The correct answer is A, 32. An IPv4 address, which is what the question means by an IP address, is thirty-two bits long. It is written in dotted-decimal form as four numbers separated by full stops, and each number stands for eight bits, or one octet, so it can run only from 0 to 255 — for example 192.168.1.1. Thirty-two bits give about 4.3 billion possible addresses, and because these began to run out, IPv6 was designed with 128-bit addresses written in hexadecimal. Every IPv4 address has a network part and a host part, separated by the subnet mask, and the addresses fall in classes A to E. Option B is wrong because 24 bits is the length of the manufacturer's OUI prefix in a MAC address. Option C is wrong because 16 bits is the size of a port number. Option D is wrong because 12 bits is not the length of any address. Exam tip: IPv4 is 32 bits, a MAC address 48 bits and IPv6 128 bits.

The correct answer is A, F1. F1 is the function key that opens Help in Windows and in almost every Microsoft Office program, which is why it is the first key on the row. The twelve function keys F1 to F12 sit along the top of the keyboard and each carries a standard job. F2 renames a selected file in Windows Explorer and moves the cursor into the edit line in Excel. F3 opens the search or find box in Explorer and in most browsers. F4 repeats the last action in Word and switches a cell reference between absolute and relative in Excel, while Alt + F4 closes the active window. F5 refreshes a web page and starts a slide show in PowerPoint. F7 runs the spelling and grammar check in Word. Options B, C and D are wrong because F2, F4 and F3 do the jobs described above and none of them opens Help. Exam tip: F1 Help, F2 rename, F3 search, F5 refresh, F7 spell check, F12 Save As.

The correct answer is D, Java. Java is an object-oriented programming language, so it is the right pick for Preet. It was created by James Gosling at Sun Microsystems and released in 1995; every piece of code sits inside a class, and the language is built on the four pillars of object orientation — encapsulation, inheritance, polymorphism and abstraction. Java source is compiled into bytecode that any Java Virtual Machine can run, which is why it is described as write once, run anywhere. Option B is wrong because Pascal, written by Niklaus Wirth in 1970 for teaching, is a structured procedural language; only the later Object Pascal added classes. Option A is wrong for the same reason, since it offers Pascal as an equal choice. Option C is wrong because BASIC, made by Kemeny and Kurtz in 1964, is a simple procedural language for beginners. Exam tip: C++, Java, Python, C# and Smalltalk are object-oriented, while C, Pascal, FORTRAN, COBOL and BASIC are procedural.

The correct answer is C, Packet filtering. A packet filtering firewall works at the network layer, the third layer of the OSI model, where it reads the header of every incoming and outgoing packet and compares the source and destination IP address, the port number and the protocol against a list of rules, then allows the packet through or drops it. It is the oldest and fastest kind of firewall and needs little memory, but it is stateless: it judges each packet on its own and cannot look inside the data, so it misses attacks hidden in the payload. Option A is wrong because a circuit-level gateway works at the session layer and only checks that the TCP handshake is valid. Option B is wrong because an application-level gateway, or proxy firewall, works at the application layer and understands protocols such as HTTP and FTP. Option D is wrong because network filtering is not a recognised firewall type. Exam tip: packet filter at the network layer, circuit-level at the session layer, proxy at the application layer.