The vireo's comeback may prove that habitat along streams in Southern California is recovering from the effects of pollution,（） indicator of environmental health in a state that has lost most of its （） woodlands.

His specialty is bringing to the forefront the strange ...

单项选择题His specialty is bringing to the forefront the strange and （） acts of depravity that only the impassive and imperturbable subconscious is （） to grasp and reckon with.

If a particular vaccine is produced only by one company...

单项选择题If a particular vaccine is produced only by one company at a single facility, there is a possibility that the supply of vaccine could grow （） if the company decides to cease production.

It can not be denied that the existing resources on ear...

单项选择题It can not be denied that the existing resources on earth will be depleted, but scientists are （） to concede the inevitability of that day,（）that new energies can be found in the near future.