Answer:
D
It helps the reader to understand which layers of the atmosphere are most important. Don't cheat
It probably needs to dig in the ground for worms and grub. So it's an adaptation for finding food.
One fourth means (one half) of (one half) .
So the 18 months must be two half-lifes.
The half-life of this particular isotope is 9 months.
It is how bright is is t the observer on earth...so wuld be c!!
this any help?