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Some questions on articles:

___ San Diego fitness experts recommend thoroughly checking out several health clubs before you join one.
a. a
b. an
c. the
d. no article is needed
answer is d, but i chose c. My reason is for a specific group, use "the"

If you only want exercise classes, ___ exercise studio without weight machines and locker rooms may work for you.
a. a
b. an
c. the
d. no article is needed
answer is b, but i chose c. again, my reason is for a specific thing, use "the"
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___ San Diego fitness experts recommend thoroughly checking out several health clubs before you join one.
a. a
b. an
c. the
d. no article is needed
answer is d, but i chose c. My reason is for a specific group, use "the"

Plural nouns do not take an article when they refer to a generality.
Elephants have long tusks. (General group of all elephants)

The San Diego fitness experts recommend... (This implies that fitness experts in other cities might not recommend it.)

If you only want exercise classes, ___ exercise studio without weight machines and locker rooms may work for you.
a. a
b. an
c. the
d. no article is needed
answer is b, but i chose c. again, my reason is for a specific thing, use "the"

No, the definite article is not correct because there is no particular exercise studio that has been mentioned earlier, and there are likely many studios to choose from. So you can choose any one of the studios which has those characteristics.
Comments  
Thanks! You are awesomely helpful.