美国教育家孟禄主张的教育起源论被称为是_________起源论;而马克思主义观点认为,教育只能起源于_________ 。
The boys spent the whole morning _______ possible answers to the question.
A. discuss
B. and discussing
C. discussing
D. and discussed
Stressful environments lead to unhealthy behaviors such as poor eating habits, which ________ increase the risk of heart disease.
[A] in turn
[B] in return
[C] by chance
[D] by turns
在网上企图通过非法手段侵入他人系统,以窃取重要秘密和个人资料的人称为__________。