In the following question, one part of the sentence may have an error. Find out which part of the sentence has an error and click the option corresponding to it. If the sentence is free from error, click the "No error" option. Had she not known (1)/ about it she should (2)/ have stayed longer. (3)/ No Error (4)?

Option 2 : 2

The error is in the second part of the sentence as the modal verb ‘would’ must replace ‘should’. Let’s see how to use ‘should’, ‘could’ and ‘would’.

Use should to give advice and suggestions.
E.G. You should probably visit the doctor.

Use could as the past form of can and to make requests.
E.G. I could read and write Tamil when I was five years old.
E.G. Could you lend me a pen please?

Use would to talk about unlikely situations and to make a polite offer.
E.G. Had the train left on time, I wouldn’t have been able to catch it.
E.G. Would you like to accompany us to the party?