The question asks about the substance that has been helpful in preserving pollen as fossils. The options provided are:
The correct answer is sporopollenin. Here’s why:
Conclusion: Sporopollenin's resistance to decomposition enables pollen grains to be preserved as fossils, providing valuable information about the Earth's historical climatology and vegetation.
| 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 |