This is a letter of

A．there are many controversial issues like the right amount of sleep.
B．among many issues the right amount of sleep is the least controversial.
C．people are now moving towards solving many controversial issues.
D．the right amount of sleep is a topic of much controversy among doctors.

A．are all related to economic considerations.
B．are not as decisive as push factors.
C．include a range of considerations.
D．are more important than push factors.