苯丙素、木脂素、香豆素类化合物的合成途径是( )
A.乙酸-丙二酸途径B.甲戊二羟酸途径C.莽草酸途径D.氨基酸途径E.复合途径
参考答案:C
The little girl was too frightened _____ a word.[ ]
A. not to tell
B. not to say
C. to tell
D. to say
简述基本经济规律的地位和作用。