To find the error in this sentence divided into parts, let's analyze each segment:
The error is in part (b) "it must constant evolve," which should be corrected to "it must constantly evolve." Therefore, the correct answer is the part of the sentence containing this error.
If the price of a commodity increases by 25%, by what percentage should the consumption be reduced to keep the expenditure the same?
A shopkeeper marks his goods 40% above cost price and offers a 10% discount. What is his percentage profit?