When he picked up a large sum of money by accident, he battled with his _____ whether he should keep it or return it to the owner.
Tony failed to finished his paper on time. If he ______ me about it, I would have came to his help.
There is an increasing concern _____________ about Ebola infection. Every country has taken necessary measures to prevent it.
In the noisy crowd, I had to raise my voice to make myself ___________.
As we can see, Peter is very happy, so he___________ have passed the exam. After all, it’s not difficult at all.
—Is Bob still a volunteer? —No, but he _____. He worked for the 2008 Beijing Olympic Games.