Q.18. During which period did the first trilobites appear? a) Cambrian
b) Devonian
c) Silurian
d) Ordovician

a) cambrian

Explanation:

The first body fossils of trilobites appeared in the Early Cambrian Period, about 540 million years ago.

A. Cambrian period

Hope this helps :)

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.