1. She asked me to hold the line.

2. She asked me to hold on.
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Are both the same? Do you have some other similar expressions?

3. He handed me the document without comment.
4. She handed me the document without comments.
(Are both OK? Do we have to use the singular form or the plural form at the end?)

5. I'll grab him on the way to the airport.
6. I'll grab him on our way to the airport.
(Are both the same and grammatical?)

1 and 2 are fine; I use the expression in 2 more often than the one in 1.

3 and 4 are fine, but usually the singular form -- "comment" -- is used.

5 and 6 are fine and are the same.