单选题 You ______be too tired-you've only been working for an hour.
[A] must not [B] won't [C] can't [D] may not

【正确答案】 C

【答案解析】[考点] 情态动词否定形式的用法
[解析] 本句意为：你不可能很累——你才工作了一个小时。表示否定推测用can't。must not“禁止”，won't“不会”，may not“可能不”。