Which organisms produce seeds during reproduction?
a) algae
b) angiosperms
c) ferns
d) mosses

B) Angiosperms

Explanation:

The algae, ferns and mosses all produce spores while conducting the asexual mode of reproduction. The seeds are produced by flowering plants called as angiosperms. The seeds are the produced by sexual mode of reproduction. These are produced by the fusion of the male gamete that is pollen and female gamete that is ovum in within the flowers of angiosperms. The fusion helps in development of zygote which is the precursor of seeds.  

i am going to guess that it is co2.