Scientists in the world are expected to find a(n) _____ to the problem of over population.

A．Tolerance is vital to friendship.
B．Friends are usually interdependent.
C．Friends do not rely financially on each other.
D．Annoying habits are worse than promise breaking.

A．People use it to sweeten food.
B．It gives us much-needed energy.
C．People take too much of it.
D．It is actually a kind of honey.