ANSWER
B.
Explanation : it’s B because the control rods used are usually made of boron which boron is a non fissile material hence won’t undergo fission when bombarded or collided with neutrons.
An Insulator.
Insulators prevent flow of electric current. Example is wood, clay.
It is 0.720 meters cause if the manufacturers of liters contain 2.27 inches it would make a deeply filled of 0.660