Endospores

a. are reproductive structures of some bacteria

b. are dormant, resistant cells

c. occur in some archae

d. appear purple in a gram stain

The correct answer is b. are dormant, resistant cells.

Explanation:

Endospores are structures that bacteria develop in order to protect their genetic material. These structures are very strong and resistant to extreme conditions such as heat, acidity, and lack of nutrients. The position of these endospores is a character for classification.