1. The earth goes around the sun.

2. The eatth moves around the sun.
3. The earth goes round the sun.
4. The earth moves round the sun.

(Which one do I have to use?)

5. Many boys were sitting around the lake.

6. Many boys were sitting round the lake.

(Do I have to use 'round' or 'around'? Which one is right in Sentence 5 and Sentence 6?)

7. Poor people are not always miserable.
(In this sentence is 'people' a common noun or a collective noun?)

8. However hard a problem it may be, you have to solve it.

9. However strong a man he may be, he can not lift the rock.

10. However rich a man he may be, he can not buy the building.

(Are the three sentences grammatical? Can we use 'is' instead of 'may be'?)

1 answer

1 and 2 are best.

5 is best.

The word "round" is an adjective that describes the shape of a circle. The word "around" is mostly used as an adverb or a preposition, as you have used it in your sentences.

7 - In that sentence "people" is both a common noun (not referring to any one person by name) and a collective noun; thus the plural verb form that goes with it.

8 - 10 are fine as they are; don't substitute "is."