Which statement best describes the role of lichens in ecological succession? A. They replace smaller trees and shrubs that need less sunlight.
B. They release acids that help break down bare rock to form soil.
C. They add nutrients to the soil and hold the soil together with roots.
D. They use nitrogen from the air to make nutrients that plants can
use.

B: They released acids to help break down bare rock to form soil.

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8