Generally speaking， ______ according to the directions，the drug has no side effect．

A．when taking

B．when taken

C．when to take

D．when to be taker

TB/T2658.9—1995标准规定：钢轨探伤作业应遵循“接头（焊缝）站，小腰慢，大腰匀速探”的要领，同时应做到仪器和手工相结合。