Female birds lay their eggs,thereby facilitating flight by reducing weight.Which "strategy" seems most likely for female bats to use to achieve the same goal?

A)lay shelled eggs
B)limit litters to a single embryo
C)refrain from flying throughout pregnancy (about 6 weeks long)
D)give birth to underdeveloped young, and subsequently carry them in a pouch that has teats
E)feed multiple embryos internally using placentas