未知题型 The U.S. Department of Agriculture played an important role in agricultural developments byA．adopting hybrid seeds and genetic engineering of plants.B．advocating the wide use of fertilizers and pesticides.C．improving the environmental conservation of lands.D．providing farmers with extension service of education.

未知题型 It is stated in Paragraph 1 that the theory of relativityA．is beyond all the current scientists' understanding.B．has failed Albert Einstein for years.C．seems at odds with the quantum mechanics.D．is useful in holding big things together.

未知题型 Douglas Gentiles research tends to testA．whether video games can produce long-term impact on the youth.B．the effect of playing pro-social games on the youth.C．whether the youth are able to classify different video games.D．the effect of playing violent games on the youth's moral fabric.