Why the big earthquakes happen after a longer period of no earthquakes?

The largest earthquakes on Earth occur at the interface between the two plates, called the megathrust.  Earthquakes are caused by movement over an area of the plate interface called the seismogenic zone. This zone 'locks' between earthquakes, such that stress builds up.

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e