Classified by different aims, there are at least 4 major types of test, among which _______ is to discover what the testee already knows about the target language.

A．George Eliot
B．O. Herry
C．Thomas Hardy
D．James Fenimore Cooper

A．The production of solar light and heat.
B．The physical and chemical nature of life.
C．The conversion of Hydrogen to helium.
D．Radiation in the X - ray part of the spectrum.