If you were standing at sea level measuring the air pressure, you would actually be measuring the air's
friction
speed
weight
moisture

Weight of air per unit area is pressure due to atmosphere. So here correct answer is Weight

Explanation:

As we know that air pressure is given by

now we know that force here due to air is due to the weight of the air

so here in order to calculate the weight we will have

here we know that

Ah = volume of air above the point where pressure is to be calculated

now from above formula we have

so here we can say that pressure is due to weight of air

i think the answer is a, hope this : )