斜视图一般按向视图的配置形式配置，在斜视图的上方必须用字母标出视图的名称，在相应的视图附近用_____指明投射方向，并注上同样的_____。
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局部视图中，一般用波浪线表示断裂边界。波浪线可以超出机件实体的投影范围。（ ）
A. 对
B. 错
当局部视图按基本视图的配置形式配置，中间又没有其他图形隔开时，可以省略标注。（ ）
A. 对
B. 错
During DNA cloning which of the following is not a crucial requirement? ____________
A. DNA inserts
B. Vector
C. Protein expression
D. Molecular cutter
Which of the following statements is correct regarding S1 nuclease? ____________
A.It acts on double stranded DNA
B.It acts on single stranded DNA
C.It acts on both types of strands
D.It is obtained from coli
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