Final answer:
The primary infection rate of chickenpox in pregnancy is not specified by options a, b, or c. The correct answer is option c. None of the above.
Step-by-step explanation:
The primary infection rate of chickenpox in pregnancy is not specified by options a, b, or c. Chickenpox is caused by the varicella-zoster virus and is the first infection with the virus, which remains latent in the body. The risk for chickenpox primary infection can occur at any gestational age during pregnancy. Therefore, the correct answer is option c. None of the above.