Which air pressure reading is likely an indicator of clear weather?
a. 900 mb
b. 950 mb
c. 1000 mb
d. 1050 mb

1050 mb of air pressure is likely an indicator of clear weather. The correct option among all the options given in the question is option "d". In reality, higher pressure is mostly associated with clear and good weather while stormy or bad weather is often associated with low air pressure. 

Awoodchuck would chuck all the wood he could chuck if a woodchuck could chuck wood.

If its history of, then b) because a) implies only present day (now)