Sun appears red at sunset because

The correct answer is C, lateral meristem. The lateral meristem, better known as the cambium, lies as a ring along the length of the stem and root and divides to add new xylem on its inner side and new phloem on its outer side, so the stem grows thicker year after year; this is secondary growth, and it is what produces the wood of a tree. Option A is wrong because the apical meristem sits at the tip of the root and the shoot and adds to length, which is primary growth. Option B is wrong because the intercalary meristem lies at the base of leaves and at the internodes and lets grasses and bamboo grow again after cutting or grazing, again adding length. Option D is wrong because permanent tissue is made of cells that have lost the power to divide and have taken a fixed shape and function. Keep the three meristems as a set: apical for length, lateral for girth, intercalary for regrowth.

The correct answer is B, blood. Blood is classed as a connective tissue because its cells lie in a matrix, and because that matrix, the plasma, is liquid it is called a fluid connective tissue; the red cells, white cells and platelets float in it and it connects the organs of the body by carrying gases, food, wastes and hormones between them. Option A is wrong because cartilage is a connective tissue too, but its matrix is solid and flexible, not fluid. Option C is wrong because epithelium is a covering and lining tissue with its cells packed tightly together and almost no matrix between them. Option D is wrong because nervous tissue is made of neurons specialised to conduct impulses and is a separate one of the four animal tissue types. Lymph is the second fluid connective tissue and is the usual second option in a two-statement version of this question.

The correct answer is A, cardiac muscle. The muscle of the heart shows light and dark bands under the microscope, so it is striated, yet it is not under the control of the will and it contracts rhythmically without rest for the whole of life, so it is involuntary; this unusual combination is exactly why it is asked. Option B is wrong because skeletal muscle is striated but voluntary, moving when the person wills it. Option C is wrong because smooth or unstriated muscle, found in the walls of the alimentary canal, blood vessels and urinary bladder, has no bands and is involuntary, so it fails the striated half of the question. Option D is wrong because the biceps is a named skeletal muscle of the arm and is therefore voluntary. Remember the three-line table: skeletal, striated and voluntary; smooth, unstriated and involuntary; cardiac, striated and involuntary.

The correct answer is C, nerve cell. A neuron carries a long process called an axon, which in a human being may run from the base of the spine to the toe, so a single nerve cell can be about a metre long; this length lets one cell carry an impulse over a great distance without any relay. Option A is wrong because the red blood cell is a small biconcave disc of a few micrometres, and in mature form it has no nucleus at all, which leaves more room for haemoglobin. Option B is wrong because a skeletal muscle fibre is indeed long and multinucleate, but shorter than the longest neuron, and it is the second choice examiners place as a distractor. Option D is wrong because a bone cell, the osteocyte, sits in a small cavity called a lacuna and is compact. Two companion facts are worth carrying: the smallest cell known is Mycoplasma and the largest single cell is the egg of an ostrich.

The correct answer is B, xylem. Xylem is a complex permanent tissue of tracheids, vessels, xylem parenchyma and xylem fibres; the vessels and tracheids are dead, hollow and joined end to end, which makes them ideal pipes for carrying water and minerals from the root to the leaves in one direction. Option A is wrong because phloem conducts the food prepared in the leaves and moves it in both directions, upward and downward, to wherever it is stored or used. Option C is wrong because collenchyma is a simple permanent tissue that gives flexibility and mechanical support to young and climbing stems; it conducts nothing. Option D is wrong because cambium is a lateral meristem whose business is division, adding new xylem inward and new phloem outward and so increasing the girth of the stem. A useful memory aid is that only the parenchyma is alive in xylem, while in phloem only the fibres are dead.