Can anyone help me with this please

In which situations is the principle of cross-cutting relationship useful in determining relative age?

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?

What processes would you expect to be key in the production of yogurt ?