—He's really a hard-working boy.
A:was still
B:was always
C:was actually
离子
K+
Na+
Mg2+
Ca2+
NO3﹣
H2PO4﹣
SO42﹣
Zn2+
培养液浓度/mol•L
1
2
0.25
活细胞内合成酶的原料是( )
I can play the guitar and I ________ play the drums.