What is a spore?

a. a reproductive cell produced by slime molds

b. a large, moving community of slime molds

c. an amoeba-like cell that digests fungi and bacteria

d. a protective wall that forms around a slime mold

Ascience research group is testing a new type of plant food. one trial is conducted in a controlled experiment. the data from the trial show that the plant that received the new food grew faster than the control plant. the group announces that the new plant food makes plants grow faster. what is the main weakness in this scientific claim?