A．were far from a panacea in all cases
B．were feasible in their recipient countries
C．failed to work in their recipient countries
D．were rejected unanimously by Asian countries

A．Because they cannot be eradicated by herbicides.
B．Because all selective herbicides can encourage the growth of previously unimportant weeds by eliminating their competitors.
C．Because they were hardly considered before so that their seeds were not prevented from germinating.
D．Because they benefit greatly from the fertilizer applied to the farm lan