nikhil.jones.s wrote:
I understand the fact that in B) 'are a force' is unidiomatic but what about 'rates for liability insurance' in C). Isn't that unidiomatic as well? As in, 'the rate of attrition' is right and not 'the rate for attrition'. Kindly help me through this.
"rates for" and "rates of" are both idiomatic: it depends on the subject. If the subject is a price "rates for" is correct, is the subject is a measure/rate "rates of" is correct ('the rate of attrition')
However this idioms are not tested with high frequency, so you can arrive at the correct answer without knowing the difference; just keep in mind that just because you know that "the rate of" is idiomatic, it does not mean that a change in the words makes the construct unidiomatic: there can be multiple correct versions of the thing (as here "rates of/for").