The first germinal layer formed in the human embryo is . . . . . . .

Choose the incorrect pair:

Thalidomide is a non-barbiturate sedative drug which was given to pregnant women. Its use was withdrawn in $1961$ because it resulted in phocomelia. This condition illustrates:

Select the odd one out.

Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?

If after ovulation no pregnancy results,the corpus luteum