Can someone tell me the last question or fill in the blank and tell me if the ones I put in are correct

What molecules does hemoglobin decay into over time

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?

Achange in direction without a change in speed is called velocity