Which of the following statements is true? 1. nitrogen is important for plant life, but not for animal life. 2 .oxygen is the most abundant gas in the atmosphere. 3. iron is an important element in chlorophyll. 4. carbon readily forms bonds because it only has four electrons in its outermost shell.

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?