Copies of chromosomes are called platelets.

sister chromatids.

macrophages.

stem cells.

 Option 'b' is correct.

Explanation:

Dichotomous key is a method to identify organisms with the help of process of answering yes or no and is mostly used by biologists.

So, Those question asked in a dichotomous key have two options :

1) Yes

2) No

Among the options, Are the insect’s antennae longer than its head? has yes or no answer.

Remaining options have long answers instead of saying yes or no.

Hence, Option 'b' is correct.