题干
An engineer has designed _______ robot that can work in _______ deep sea to clean waste.
A：a; the
B：a; a
C：/; the
D：the; /
答案(点此获取答案解析）
A
H+
Li→2
He。根据以上信息，以下判断正确的是_________（填入选项前的字母代号）