—No. He learns English _______.
A:by himself
B:for himself
C:with himself
— How do you like the regulations of our school?
— The regulations are strict with the students and they require that students _______ at least 90% of the lectures.
蔗糖溶液
a
b
c
d
葱茎形态
写出笔顺。
兆:____
煮:____
____ ____ ____ ____
①α∥β⇒l⊥m;
②α⊥β⇒l∥m;
③l∥m⇒α⊥β;
④l⊥m⇒α∥β
其中正确命题的序号是____.