One important development during the 3rd trimester that will insulate the infant against changes in temperature is a. the deposition of fat under the skin b. the closing of the septum between c. the atria of the heart d. the beginnings of lung functioning e. the beginnings of light and sound sensing

The correct answer is a. the deposition of fat under the skin

Explanation:

After 28th week the third trimester starts in a pregnant woman which last until the baby gets delivered which is around 40th week. In this period the baby grows in size and fats get stored under the skin of the baby.

As fat is a good insulator it provides insulation to the infant against the changes in the temperature so it is one of the important development during the 3rd trimester. As the baby grows bigger in this period it put pressure on organs which might cause difficulty in breathing for mother. Therefore the correct answer is a.