The correct option is B Snake
The amnion is a membrane that when first formed, closely covers the embryo. It fills with the amniotic fluid which causes the amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo. It is a feature of amniotes which includes reptiles, birds and mammals.
Of the given options, snake is the only one which fits in this category (as it is a reptile).
Therefore, the correct answer is option B.