Answer:
B.convection currents in the mantle
Explanation:
<span>They are balanced. If the forces were not balanced the book would move*. In this example, the downward force of gravity on the book is counterbalanced by the upthrust of the desk. </span>
Distance , d = a+b

The unit of d is in meter and t is in seconds.
So the unit of a a must be meter.
Now we have unit of b

is meter.
So unit of b*

= meter
Unit of b = meter/

So unit of a = m and unit of b = m/

.
Combustion Engine Exhaust----Cars, trucks, jet airplanes and other combustion engine vehicles cause air pollution. The exhaust from these contains carbon monoxide, nitrous oxide and gaseous oxide. This type of air pollution creates smog
Assumes the shape and volume of its container
<span>particles can move past one another</span>