There are three specific types of stress.
Compression occurs when pressure pushes in on an object from opposite sides this happens slowly.
Tension occurs when pressure pulls on opposite sides of an object, causing it to stretch this happens quickly.
shear occurs when two objects try to slide past each other in opposite directions this happens not to fast but not to slow.
The mass number goes on top, and the atomic number goes on bottom.
Therefore, the answer is C:
40
K
19
Due to it's electronic configuration w/c is 1s2 2s2 2ps 3s1 considering the last w/c is 3s1, sodium should be in row 3 period a1.