A.open () requires a second argument

B.instd, outstd, errstd are the names of pre-opened streams

C.open () is a function which returns an object that represents a physical file

D.if invoking open () fails, an exception is raised

A.11

B.the variable becomes unavailable

C.10

D.9

A.it outputs 3

B.it raises an exception

C.it outputs 0

D.it outputs 'None'

A.it outputs 2

B.it raises an exception

C.it outputs 1

D.it outputs 0

A.B.VarA == 3

B.isinstance(obj_c,A)

C.obj_b.prop_a == 3

D.hasattr(obj_b, 'prop_aa')