Which element is the basis for all living things and can combine with other elements in many ways? phosphorus carbon oxygen sulfur

The right answer is carbon.

All living things are made of carbon skeletons. These molecular carbon skeletons form most of the tissues and proteins that make up living things. So much so that carbon chemistry was called "organic" chemistry because it was a direct result of the observation of living organ compounds. All foods produced by agriculture and  consumed by man (carbohydrates, lipids, proteins) are at the base of the carbon chains.

b carbon

Explanation:

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the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.