Questions

The P wave in the ECG represents atrial depolarization, which results in atrial contraction, or atrial systole.

The P wave is a summation wave generated by the depolarization front as it transits the atria.

Pinctada vulgaris is a bivalve from which pearl is obtained.

The given statement that a calorie is another term for carbohydrate is False.

Carbohydrates are one of the main types of nutrients, and are most important source of energy.

Where as Calorie is a measurement of how much heat energy is generated by the body processing food.

Your digestive system changes carbohydrates into glucose(blood sugar). Your body uses this sugar for energy. 

River.

It always runs  or flows but never walks.

It will sound like murmuring but never talks.

It has bed but never sleeps.

It has mouth but never eats.

True, The luster of a metal is due to presence of free electrons. Luster means shine or soft glow. We know that metals have the quality of reflecting light from its surface.