Can someone answer this ASAP ! Please

Could someone me with number one you

Why do oceanic plates tend to subduction when colliding with a continental plate

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?