Iodine test is shown by

Starch

The answer is (1) starch.

Iodine test is a chemical test used to detect the presence of starch. When iodine is added to a starch solution, it forms a blue-black complex. This is because the iodine molecules can fit into the helical structure of starch molecules.

Glycogen, polypeptides, and glucose do not have the same helical structure as starch, so they do not give a positive iodine test.

Therefore, the only option that is a carbohydrate that gives a positive iodine test is starch.

Here are some other examples of carbohydrates that give a positive iodine test:

• Dextrin
• Maltodextrin
• Cellulose
• Amylopectin