All the boys / All boys

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. All the boys and girls were singing the national anthem.
  2. All boys and girls were singing the national anthem.
    Which sentence is more appropriate?
    Thanks.
2

Both are possible.
Using ‘the’ indicates a specific group of boys and girls.
Common sense therefore, indicates that this is the most appropriate in the majority of situations, as usually a sentence such as yours would be used by someone referring to a particular group.
However, ultimately it depends on context

3

There is a bit of a clash in this sentence:

.

because the absence of the article ‘the’ suggests that this would be a regular/habitual process but the tense ‘were singing’ suggests otherwise. This absence of the article would work if the tense was in a simple form as:

All boys and girls sing/sang the national anthem

4

Good point.