单项选择题 某企业盈亏临界点销售量为3 000件，预计正常销售量为5 000件，则盈亏临界点作业率和安全边际率分别为（      ）。 A、30%和70% B、55%和45% C、60%和40% D、62.5%和37.5%

单项选择题 潮州筝的特点是声情并茂，音韵变化微妙。特色技法是“双4”、“双7”和活五调的“双2”。

单项选择题 Identify the fallacy in the following statement: Every time the cheerleaders have worn blue ribbons, the basketball team has won. If the team wants to keep winning, the cheerleaders should continue wearing blue ribbons.