<p>Many times we see problems with these words because they are vague, but when there is absolutely only one noun in the sentence it could be referring to, would it be appropriate to allow 'it' in the sentence? </p>
<p>Just want to clarify that because numerous times a mistake is a mistake because it is 'vague' when, I suppose in normal conversational speech, is quite obvious what it's referring to. I do know how to identify these but just yesterday, I started to overthink some of the questions. Help?</p>
<p>It is perfectly OK to use ‘it’ in a sentence when the referent is clear. What you need to watch out for is when the grammar of the sentence dictates one referent, and the logic of the sentence (or the context) dictates a different referent.</p>
<p>“I went to the store after it opened” is grammatically and logically clear.</p>
<p>“I walked through the door at the store after it opened” is grammatically ambiguous.</p>
<p>Note that sometimes the referent is actually in a prior sentence, and that is OK too as long as it isn’t grammatically ambiguous.</p>
<p>Thanks Green 
yeah, i got you and makes sense. perhaps feeling a lil anxious before the big test is the reason for my sudden doubting.</p>
<p>If you are only using one subject in a sentence, it is assumed that the pronoun that follows refers to the subject. If you are using two (or more) subjects in a sentence or compound sentence, use the noun and not the pronoun to clarify.</p>
<p>Example of improper pronoun use: Mary did not know that Susan was late, her phone broke.</p>
<p>Above, “her” can refer to Mary or Susan, but it is not clear which. Avoid these sentences.</p>