单项选择题 Current estimates put thirteen percent of global flora at risk of extinction, but this number does not include （） plants from tropical regions, where the majority of the world's plants grow.

单项选择题 The teacher has （） catering to some students, but to retain his tenure, which effects only after a teacher has unanimously gratified his students, he offers his complaints （）.

单项选择题 Although scientists have long （） the human appendix as （）organ, there is a growing body of evidence indicating that the appendix does in fact have a significant function as a part of the body's immune system.