Terrestrial vertebrates use the urea cycle to convert the ammonium ion to urea such that the urea can be excreted. In the production of urea, only one of the nitrogens in the product comes from ammonium ions. What is the source of the other nitrogen?a. Another molecule of glutamate
b. Aspartate
c. Fumarate
d. Carbamoyl phosphate

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus