Which life-form was most abundant 250 million years ago?

a. dinosaurs
b.reptiles
c.bony fishes
d.trilobites

I think it's d.

well, they were abundant until they died out about the 250 million years ago.

then what is it supposed to be, reptiles?

I would do with d, assuming they didn't die out then, but at 249million years ago.

oh ok

Trilobites became much less abundant earlier, see here:

http://en.wikipedia.org/wiki/Trilobite

They died out completely 250 millions years ago.

To determine which life-form was most abundant 250 million years ago, we can consider the geological time period known as the Permian. During this period, the Earth experienced a significant event called the Permian-Triassic extinction event, which resulted in the extinction of many species.

Among the given options, trilobites were not the most abundant life-form during this time. Trilobites were marine arthropods that thrived from the Cambrian period until the Permian period, but they became extinct before the Permian extinction event.

Dinosaurs, reptiles, and bony fishes all appeared after the Permian extinction event. Dinosaurs became dominant during the Mesozoic Era, which started after the Permian period. Reptiles, including dinosaurs, were present during the Permian period but were not the most abundant life-form. Bony fishes also originated during the Mesozoic Era and were not prevalent during the Permian period.

Considering this information, option b. reptiles is the correct answer. Although dinosaurs were a type of reptile, they became dominant later in the Mesozoic Era.