Missing options:
a. low pressure system
b. circulatory system
c. arctic system
d. high pressure system
Answer:
a. low pressure system
Step-by-step explanation:
A low-pressure system is always associated with more clouds, thunderstorms, and also the development of swirling air masses such as tornadoes and cyclones. Principally, the low-pressure system develops when the atmospheric pressure drops compared to the surroundings at the sea level. Therefore, air masses come from surroundings and allows the development of extensive clouds causing thunderstorms; if pressure drops further, it allows the air masses to swirl and make tornadoes or cyclones. This is also the reason that the development of a low-pressure system is known as cyclogenesis.
By contrast, the high-pressure system avoids the formation of clouds because the possibility of air masses divergence is pretty low.