Whenever I go to Beijing, ____ is quite frequent, I will go to visit the Great Wall.

He__________ he would be able to leave tomorrow, but it’s beginning to took difficult.

Can you work out the maths problem?— Sorry, I can ______ understand its meaning.

In the dark street, there wasn’t a single person _____ she could ask for help. [ ]

Mrs Zhang has taught ______math for three years and she teaches very well.