Read the following passage and mark the letter A, B, C, or D on your answer

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
Despite the wealth of information campaigns telling people about global warming and its causes, most people have (23) .................. to realize how severe the problem is. Coming climate changes could alter as much as one third of plant and animal habitats by the end of the 22nd century. These changes could in (24)..................cause widespread extinctions among plant and animal species around the globe.
Coastal and island habitats are perhaps in the greatest danger (25) .................. they face the combined threats of warming oceans and rising sea levels. As habitats change, many animals will come under intense pressure to find more suitable homes for themselves. Mass (26).................. of at least some animals are certainly to be expected, but the fact remains that many animals will simply not be able to move fast enough.
Such dire predictions may sound alarmist, but they are based on the rather moderate estimate that the amount of carbon dioxide in the atmosphere will double by 2100. Many scientists believe, however, that this figure is actually very conservative, and they claim that a tripling is far more realistic. If they are (27) .................. , the effects on nature will be even more dramatic.
(Source: https://www.nytimes.com/interactive/2017/climate)