Some people are worrying about the possibility ________ mobile phones could be responsible for a range of illnesses, from rashes(皮疹) to brain tumors

下列句中划线的文言实词，解释正确的一项是（ ）

I lost my notebook. I must ______ it.

I don’t think he＿＿＿＿＿＿＿ a new bike.

Shen Xue and Zhao Hongbo won the gold medal for Chinaso we’re proud ___ them.