Help me with the usage of "the" and commas

[Imsriram]

Our work involved [the] complete design of a transformer.

Do you have books?
Do you have [the] books?

Both make sense to me. The second sentence suggests that the reader knows something about the books.

I was involved in [the] testing and verification of the satellite.

Can we use “the” before scientific principles?

I want to learn about [the] gravitation.

My main goal is to learn and [to] earn first rank in the exam.

Can we combine singular and plural objects?
" I need an apple and many bananas"

Comma before “using” needed?

I designed the car when I was working, using several tools.

Thanks

[Luschen]

@Imsriram

Our work involved [the] complete design of a transformer.

[color=red]Correct - this is a specific instance of design - compare it to:

“Our work involved designing transformers.”

Do you have books?
Do you have [the] books?

Both make sense to me. The second sentence suggests that the reader knows something about the books.

[color=red]{in the second, he is talking about specific books}

I was involved in [the] testing and verification of the satellite.

{This was a specific task involving a specific satellite. Once again, compare to “I was involved in testing and verifying satellites.”

Can we use “the” before scientific principles?

I want to learn about [the] gravitation.

[color=red]Yes, if it is a specific case of gravitation: “I want to learn about gravitation.” “I want to learn about the gravitation of the Sun.”

My main goal is to learn and [to] earn first rank in the exam. \

[color=red]I think the second to is optional.

Can we combine singular and plural objects?
" I need an apple and many bananas"

[color=red]Yes

Comma before “using” needed?

I designed the car when I was working, using several tools.

[color=red]Yes

Thanks