Identifying Variables

Analogy- 1 is to arete as 5 is to cirque horn glacial valley hanging valley

According to the big bang theory, after the "bang," the universe remained dark until about  300,000 yearsone billion yearsthree minutesthree billion years  later, when neutral atoms began to form.

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?