A:①②
B:①③
C:②③
D:①④
正数a、b、c满足abc=a+b+c+2,求证:a+b+c≥4(1a+1b+1c)
下列有关基因工程技术的叙述,正确的是( )
—Catherine, I have cleaned the room for you.
— Thanks. You _______ it. I could manage it myself.