A.) 5
B.) 6
C.) 7
D.) 8

C. 7

Step-by-step explanation:

First you have to find the unit rate of this equation

The unit rate is 20 students for every 1 teacher because 40 divided by 2 is 20

so if you do 140 divided by 20 your answer is 7

there are 7 teachers

the answer is: d) o, f, and kr.

atomic radius of bromine (br) is 114 pm.

atomic radius of oxygen (o) is 73 pm.

atomic radius of fluorine (f) is 72 pm.

atomic radius of krypron (kr) is 112 pm.

the atomic radius of a chemical element is a measure of the size of its atom.

the atomic radius varies with increasing atomic number, but usually increases because of increasing of number of electrons.

the atomic radius decreases across the periods because an increasing number of protons, because greater attraction between the protons and electrons.