However, at times this balance in nature is disturbed by human activities, _______ a number of possibly unforeseen effects.

You mustn’t swim here. Look at the sign. It ______ “No swimming.”—Oh, I didn’t notice it. Thanks for telling me.

What is the most important ________ in a day—Breakfast.

At times, parents find it difficult __________ with their teenage children.

I wish I ____fly to the moon one day