Answer:
Option A, Key stone
Explanation:
A keystone species plays a major role in an ecosystem as it is the species whose presence effects all other species in the ecosystem .In general a keystone species is always a dominant predator that feed on prey population. If it is removed, the prey population will explode and the population diversity will reduce. For example - bison, prairie dog etc.
Hence, option A is correct
The speed of sound wave is slower than electromagnetic wave.
Clouds can block light and heat from the Sun, making Earth's temperature cooler. You've probably noticed this kind of cooldown on a cloudy day. However, some heat from the Sun does get down to Earth. Clouds can trap that heat from the Sun.
The answer is A: The rough ER has visible ribosomes.
The answer is C. It's kind of like how humans speak in different languages. So do birds. They may make different noises but they are all still birds.
