[Q]: The growth of which of the following usually occurs first in primary succession on a bare rock?
===
****
[A]: Lichens

[Q]: A sound is heard when you pluck a string on a guitar. What will happen to the sound if the same string is plucked harder?
===
****
[A]: The pitch will stay the same, and the volume will be higher.

[Q]: Which situation is the best example of ecological succession?
===
****
[A]:
One species replaces another species in an ecosystem.