You are supposed ________ the work yesterday but you forgot.

Why? Where is the key to the meeting room?– Dear me! You ______ it in the taxi![ ]

She __________ have left school, for her bike is stillhere.

Which team do you think will win the game—The team B has better players，so I________they will win

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