Why might you want to use a single fixed pulley?
to raise or lower heavy objects
to raise or lower lightweight objects
to reduce the force needed to raise objects
to reduce the weight of lifted objects

A single fixed pulley can be used to raise or lower lightweight objects.

Option b

Explanation:

A pulley is a simple machine tool which is used to make lifting or lowering tasks easy.  A single fixed pulley is a system involving only one pulley fixed on a constant rigid support with a rope wrapped around the wheel. Such a system can be used only to change the direction of  applied force in raising or lowering small, lightweight objects which need minimal work force.

A single fixed pulley system helps only in redirecting the applied force direction by using a rope and wheel assembly. The work done in such a case remains the same and hence it is not preferred to use it in lifting heavy objects. Neither is the required force reduced in case of a single fixed pulley system. A movable pulley helps in achieving (A) and (C).

a high pressure system is a dense air mass that is usually cooler and drier than the surrounding air. a low pressure system is a less dense air mass that is usually wetter and warmer than the surrounding air.

in general, areas that experience high atmospheric pressure also experience fair weather. low pressure systems can cause the formation of clouds and storms. air usually flows from areas of high pressure to areas of low pressure..

measure their densities same density, same sub