C. set off D. run out

【点拨】由when Mitchell retires可以推测，Briggs将会"接任（take over）"总经理的职务。get away逃脱，离开；set off出发，使爆炸；run out用完，耗尽。

3. barrier

【用法】barrier是名词，意为：①栅栏，屏障，障碍物；②障碍。如：

Fans broke through the barriers and rushed onto the field.

Disability need not be a barrier to a successful career.

【考例】 Carbon dioxide, which makes a _____ between us and the sun, prevents heat from getting out of the atmosphere easily, so the earth is becoming warmer. (湖北2013)

A. difference B. comparison

C. connection D. barrier

【点拨】由prevents heat from getting out of the atmosphere可以推测，二氧化碳在我们和太阳之间形成了一个"屏障（barrier）"，故选D项。difference不同，差别；comparison比较，对照；connection联系，连接。

4. procedure

【用法】procedure是名词，意为"程序，步骤，手续"。如：

Companies use a variety of testing procedures to select appropriate candidates.

【考例】The officer insisted that Michael did not follow the correct _____ in applying for a visa. (湖北2012)

A. pattern B. procedure