Question

Thank you all for _____ _____ in our volunteer work.

1. Fill in the blanks with suitable expressions.

2. Put two English words in the blanks.

3. What are the appropriate words for the blanks? Complete the sentence by putting right words in the blanks.

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Are the directions correct and commonly used? Which directions do we have to use?

Answer 1

I would use 2 and maybe 3, but not 1. The word "expressions" implies phrases or sentences, not single words.

Answer 2

"Thank you all for helping us in our volunteer work!" And I would use 2.
There you go hope it helps!