Just scan the operands from right to left and try to keep inside parantheses and update the parentheses as per requirement .
Step1 : (F+G)
Step2:(D-E) (F+G)
Step3:((D-E)*(F+G))
Step4:(skip C for now as we don't get any operator for the consecutive operands i.e. for BC)
Final Step:((A+B)*C)-((D-E)*(F+G))
Hence , Option B is correct.