Assertion A is true because ATP is indeed used at two steps in glycolysis. These steps are the conversion of glucose to glucose-6-phosphate, and the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate. In both of these steps, a phosphate group is added to the substrate, and ATP is used to provide the phosphate group.
Reason R is also true and provides the correct explanation for Assertion A. The first ATP is used in the conversion of glucose to glucose-6-phosphate, and the second ATP is used in the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate. Therefore, Reason R correctly explains why ATP is used at two steps in glycolysis.
Therefore, The correct answer is (D): Both A and R are true and R is the correct explanation of A.

| Pair of skeletal parts | Category | |
|---|---|---|
| (a)$\,\,$ | Sternum and ribs$\,\,$ | Axial skeleton |
| (b)$\,\,$ | Clavicle and glenoid cavity$\,\,$ | Pelvic girdle |
| (c)$\,\,$ | Flumerus and ulna$\,\,$ | Appendicular skeleton |
| (d)$\,\,$ | Malleus and stapes$\,\,$ | Ear ossicles |
It is the process in which glucose is broken down to produce energy. It produces two molecules of pyruvate, ATP, NADH and water. If the process takes place in cytoplasm of a cell and it does not require oxygen. It occurs in both aerobic and anaerobic organisms.
