A student asked this question today. She’s doing passive voice. In her book, it says to use “seen,” you have to do:
S+ be + seen + to + Verb
Example: “She was seen to run into the room.”
She got this question:
He was seen ______ the restaurant with a foreigner yesterday.
A) enter into
B) entering
C) to enter into
D) entering to
She put down C. The teacher said it’s B. I say it’s both.
What is it? And why?
Thanks. 
One is to report how an action occurred.
She was seen to enter the restaurant.
One is to report the use of your eyes.
She was seen entering the restaurant.
To contrasts that:
She was heard to have sung that song.
She was heard singing that song.
Or something like that. I think that’s the distinction.
It’s both.
Both “to enter” (infinitive) and “entering” (gerund) are tenseless.
In fact, in the US, we would preferentially use ©. (b) sounds somewhat affected to my ear, though not ungrammatical.
Good grief. I hope this lesson includes a section on why you should not use the passive voice unless there’s an extremely good reason.
Anyway, I agree that both answers are (grammatically) correct, but to my ear sentences like “She was seen to run into the room” are downright weird. You are left wondering what, exactly, the writer was trying to clarify in using such a clumsy sentence. It’s weak and somewhat ambiguous.
[quote=“ironlady”]
In fact, in the US, we would preferentially use (c). (b) sounds somewhat affected to my ear, though not ungrammatical.[/quote]
That’s funny, I’m American and I think the opposite 
[quote=“Fox”]
Or something like that. I think that’s the distinction.[/quote]
Yep. I might say “to report that an action occurred” and “that an action was occurring.” If someone was “seen to enter” something they definitely entered it. “seen entering” doesn’t mean that the action was completed. The perpetrator may have been apprehended while entering, for example. It all sounds like police-ese to me.
[quote=“louisfriend”][quote=“ironlady”]
In fact, in the US, we would preferentially use (c). (b) sounds somewhat affected to my ear, though not ungrammatical.[/quote]
That’s funny, I’m American and I think the opposite [/quote]
Me too, but I’m a limey so what would I know?
Also a fan of B. Glad to know they are both ok.
To people asking what the point is: in Taiwanese public schools, the point of grammar is to have useless and confusing tests that are always full of errors. Don’t you know this?