I suppose you know you can turn into superwoman or superman in an
emergency. Mrs Pam Weldon reported that her baby nearly slipped under
the wheels of a car. Mrs Weldon weighs only 50 kilos, but she said she
lifted the car to save her baby. Dr Murray Watson, a zoologist, wrote
that he jumped nearly three metres into the air to grab the lowest
branch of a tree when hyenas chased him in Kenya. Perhaps you wonder
if you can perform such feats. The chances are that you can. Doctors
say that we can find great reserves of strength when we are afraid.
It's well-known that adrenalin can turn us into superwomen or
supermen!
Source: Longman English grammar practice, L. G. Alexander, Page 11
I looked up both superman and superwoman in many dictionaries and they all know them as countable nouns. Shouldn't there be an a before superwoman in the first line:
I suppose you know you can turn into a superwoman or superman in an
emergency.
Best Answer
Short answer: The first usage of "superman" and "superwoman" should have been capitalized, because the author is almost certainly referring to the comic-book character Superman (and his female equivalent Superwoman) which are proper nouns (and should not be capitalized).
The second usage should also not be capitalized, because they are plural and so can't then be referring to a (singular) character name.
It's possible the editor thought that since the second usage is not capitalized, the first usage doesn't have to be. Or perhaps the author was trying to make a connection between the first and last sentences of the paragraph. Either way, it's kind of an "epic fail" in an English grammar study guide.
Side note: As far as I know there is no "official" comic character called "Superwoman". There have been a number of short-term characters introduced by that name, but the female equivalent of Superman is Supergirl, who has had numerous appearances in the comics and a currently-running TV show. Note also this isn't as sexist as it might sound because A) Supergirl is a teenager, and B) there have been various comics and shows titled Superboy, mostly about Clark Kent as a young man.
I know all that might be a bit nerdy, but it is useful context to know why the use of "Superwoman", as a proper name, might sound odd to some people.