1.We use X as the ___ for an unknown quantity in algebra.
问题描述：
1.We use X as the ___ for an unknown quantity in algebra.
A.symptom
B.symbol
C.simple
D.sample
答
symptom:[ 'simptəm ]
n.症状,征兆
symbol:[ 'simbəl ]
n.符号,标志,象征
simple:[ 'simpl ]
a.简单的,简朴的,单纯的
sample:[ 'sæmpl ]
n.样品,标本
v.抽取样品
题意是：我们用X当作未知数的________
应该填当作未知数的符号.所以选B