Immediate source of energy isA.SucroseB.Glucose C.Fat D.Starch

The correct answer is B. Glucose.

Explanation:
Glucose is the primary and most immediate source of energy for cells in both plants and animals. It is a simple sugar (monosaccharide) that cells utilize in the process of cellular respiration to generate ATP (adenosine triphosphate), the molecule that directly provides energy for cellular activities.

Other substances like sucrose (a disaccharide), fat, and starch are also sources of energy, but they first need to be broken down into simpler molecules like glucose before they can be used by the body. This breakdown process takes time, which is why glucose is the "immediate" source of energy.

Let’s take a look at each option:

A. Sucrose: Sucrose is a disaccharide made of glucose and fructose. It needs to be broken down into these monosaccharides before it can be used for energy, making it not an immediate source.
B. Glucose: This is the main fuel for cellular processes, readily absorbed and quickly used by cells to produce ATP.
C. Fat: Fats (lipids) store energy long-term, but they must go through complex processes like beta-oxidation to release energy, which takes time.
D. Starch: Starch is a polysaccharide, which is a long chain of glucose molecules. It must first be broken down into glucose before it can provide energy.
Thus, Glucose (B) is the immediate source of energy.