As owning a car is helpful, it costs a lot.
Is this sentence grammatically wrong? The answer key said 'As' can't be used in this situation. But I think as can be used in many different ways.
As owning a car is helpful, it costs a lot.
Is this sentence grammatically wrong? The answer key said 'As' can't be used in this situation. But I think as can be used in many different ways.
As owning a car is helpful, it costs a lot.
This sentence is grammatically correct, but it doesn't make sense. The reason is that as in this sentence functions as a conjunction meaning because, so it means
Because owning a car is helpful, it costs a lot.
The meaning is "clause1 causes clause2", whereas the intended meaning is that clause1 is a positive effect of owning a car, and clause2 is a negative effect: although has this meaning.
Although owning a car is helpful, it costs a lot.
I agree with the answer key.
The sentence is combining two thoughts:
Because we are appending a negative to a positive, we need a word to alert the reader that a shift is coming. This would be acceptable:
Although owning a car is helpful, it costs a lot.
The word as could be used to start a sentence like this one, but we would want the second thought to reinforce the first, not provide a offsetting condition; for example:
As owning a car is helpful, it is worth the money.
In such a construct, the word as essentially means "because."
The sentence is grammatically correct. When used this way, "as" means "because". So the sentence says that cars are expensive because they are helpful. This may or may not be true, but grammar has nothing to do with whether statements are true or false.
Some of the other answers try to change the meaning of the sentence. When correcting grammar, meaning should not be changed unless you are sure the speaker had another meaning in mind. As a factual matter, prices depend on supply and demand. Part of the high price of cars is due to their demand and that demand comes from the fact that they are so useful.
If someone claims it's due to the cost of producing them and that their usefulness is irrelevant, that would be factually incorrect (and, frankly, silly). Used toilet paper is more expensive to produce than new toilet paper. But you pay for one because it is more helpful. A thirty year old broken car is even more expensive to produce than a comparable new car. Yet the new car will be more expensive because it is more helpful and thus is in more demand.