A．It increased the students’ white blood cell.
B．It increased some students’ energy level.
C．It improved the students’ ability to play musical instruments.
D．It released a natural painkiller in some students’ bodies.

A．Farmers’ rejection of his planting techniques.
B．The persistent drought throughout the country.
C．Difficulty in importing high-yielding wheat seeds.
D．The local government’s slowness in taking action.