t ______ research intoheart disease and its effects on the body, we do not have adequate substitutesfor the use of animals

I didn’t go camping on my vacation. What about you — _________.

____ is the letter from—It’s from Mike, my pen pal.

In China，it is a traditional________to show respect to ancestors during the Qingming Festival.

“You are too selfish. It’s high time you that you are not the most important person in the world.” Peter said to his boss angrily.