A. Most recent period of the Cenozoic era.
Answer:

Explanation:
÷
=
To change the ÷ sign to a × sign, swap the denominators and the numerators of the second fraction.
×
=
Directly multiply. Numerators with numerators and denominators with denominators.
Answer:
B. The bird will stop flying because it will quickly use up its remaining
energy.
Explanation:
This is because the mitochondria is known as the power house of cells. Oxidative phosphorylation takes place in this organelle and it involves the conversion of ADP to ATP through the hydrogen ions(protons).
When the hydrogen ion channel is blocked, energy production in cells stop.
This is why the bird will stop flying as it would have used up its remaining energy and won’t have a new one to use to continue flying.
Answer:
Oil
Explanation:
Since, unlike oil, source like wind, solar, water etc. come naturally we don't and can't replace them but when the viscosity in oil has been used up it must be change to allow the proper functioning of the machine.
Answer: There are 3 major problems with hydrogen as a vehicle fuel, compared to gasoline. 1 - It takes a lot of energy to produce. You have to run a lot of electricity through water to break it down to hydrogen and oxygen. ... It's most useful form is liquid hydrogen, giving far more energy content than as a highly compressed gas.