A successful scientist needs _____ if he
题型：选择题
问题：
A successful scientist needs _____ if he wants to make hypothesis (假设) of how processes work and how events take place.
A．permission
B．penetration
C．imagination
D．convention
题型：选择题
A successful scientist needs _____ if he wants to make hypothesis (假设) of how processes work and how events take place.
A．permission
B．penetration
C．imagination
D．convention
由关系R和S通过运算得到关系T，则所使用的运算为______。