The correct answer is (d) Iodine solution.

Why option (d) is correct:

Iodine solution stains starch by reacting with it to produce a characteristic blue-black color. This reaction occurs because iodine molecules fit into the helical structure of amylose (a component of starch), forming a starch-iodine complex, which results in the color change. This test is commonly used in biology and chemistry to identify the presence of starch in a sample.

Explanation for other options:

– (a) Aniline sulphate is used to stain lignin, a component of plant cell walls, and does not react with starch.
– (b) Aniline blue is used to stain collagen or plant tissues, typically highlighting cell walls and other structures but not starch.
– (c) Borax carmine is a nuclear stain used in histology, primarily for staining animal tissues, and does not stain starch.

Thus, iodine solution is specifically used for detecting starch.