Identify the error in the given sentence:
A lakh rupees are a lot of money.
A. A
B. Are
C. A lot of
D. Money

Hint: A sentence is perfect when it is constructed with proper syntax and when is has consistency of word usage and other parts of speech.

Complete step by step answer:
Option A – The article ‘A’ in the sentence gives the quantity of the noun in the sentence. In this context, the noun is ‘lakh rupees’ which means one lakh rupees. The usage of this article was not an error; hence this is not the right option.
Option B – Are is the word used to support plural nouns, but in the given sentence there is no plural noun – ‘a’ lakh rupees means the number of ‘lakh rupees’ is just one which makes it a singular noun and hence instead of are, the right word should be ‘is’. This is the error in the sentence; hence this is the right option.
Option C – ‘A lot of’ means something that is in a large quantity. This option also supports the fact that there is no plural noun in the sentence. However, this is not an error; hence this is not the right option.
Option D – Money is a noun that is being talked about, which makes it the subject of the sentence. This is not an error hence this is not the right option.

So, the correct answer is “Option B”.

Note:
Being aware of rules of grammar and understanding how they are supposed to be used in a sentence makes it very easy to identify errors just by looking at the sentence.