Layer 1 of the Open Systems Interconnection (OSI) model is,

The correct answer is B, 9. In the binary system every place stands for a power of two, and 257 is 256 plus 1, that is two raised to the eighth plus two raised to the zero. It is therefore written as 100000001, a one followed by seven zeros and another one, which is nine digits in all. A quicker way is to look for the largest power of two that fits inside the number: for 257 that is 256, so the highest place used is the ninth from the right, and every number from 256 up to 511 needs exactly nine binary digits. A is wrong because eight digits reach only up to 255, one short of 257. C is wrong because seven digits stop at 127. D is wrong because ten digits become necessary only from 512 onward. Exam tip: n binary digits count from 0 to two raised to n minus one, so 8 bits end at 255.

The correct answer is B, Meta Search Engine. A meta search engine keeps no index of its own. It hands the user's query to several other search engines at the same time, collects what they send back, removes repeated hits and shows one merged list. Because it borrows from many sources, a single search covers more of the web than any one engine would on its own. Dogpile and Startpage work in this way. A is wrong because advanced search only means the extra filters an ordinary engine offers, such as date, file type or exact phrase, while it still searches its own index. C is wrong because search tool is a loose term for any utility that finds files or text, not a defined class of engine. D is wrong because Boolean searching refers to using AND, OR and NOT inside one engine, not to querying other engines. Exam tip: meta means about, so a meta search engine searches the searchers.

The correct answer is A, HREF. The href attribute of the anchor tag carries the address the browser should open when the link is clicked, so href alone decides where a link leads. The text written between the opening and closing anchor tags is what the reader sees and clicks. The value of href can be a full web address, a path to another file on the same site, or a point inside the same page written after a hash. B is wrong because src supplies the source file for images, scripts and iframes, not for links. C is wrong because link is a separate element placed in the head section to attach stylesheets; it is not an attribute of the anchor tag. D is wrong because HYPERLINK is not an HTML attribute at all, it is the name of a spreadsheet function. Exam tip: remember the pair — href points a link somewhere, src pulls a file in.

The correct answer is C, DCL. The Data Control Language governs who may do what inside the database: GRANT gives a user a privilege such as the right to read or to update a table, and REVOKE withdraws a privilege already given. Option A is wrong because the Data Definition Language changes the structure of database objects through CREATE, ALTER, DROP and TRUNCATE. Option B is wrong because the Data Manipulation Language works on the rows themselves through INSERT, UPDATE, DELETE and SELECT. Option D is wrong because the Transaction Control Language manages a transaction as a unit with COMMIT to make changes permanent, ROLLBACK to undo them and SAVEPOINT to mark a place to roll back to. Fix the four groups by their purpose: structure, data, rights and transactions.

The correct answer is C, MongoDB. MongoDB stores data as documents in a flexible, JSON-like form instead of as rows in tables with a fixed set of columns, and it is queried through its own interface rather than mainly through SQL, which makes it the standard example of a NoSQL database in exam papers. Option A is wrong because Oracle Database is the best known commercial relational system and uses SQL. Option B is wrong because MySQL is an open source relational database, now owned by Oracle, and the M of the LAMP stack. Option D is wrong because Microsoft SQL Server is Microsoft's relational database and works through Transact-SQL. The clue in such questions is the word table: relational systems force a fixed table structure, while NoSQL systems do not.