This group of chemicals .... believed to be harmful to people with asthma.
Answer key: #2
My take: "This group of chemicals .... believed to be harmful to people with asthma."
I take out "of chemicals", it is just a modifier.
"This group .... believed to be harmful to people with asthma."
Now it is clear the missing work must be [is].
Correct me if I am wrong.
(Two separate sources that contradict each other, though:
1. you know, this is a democratic party, who just recently now was raising their arms up in air screaming about, " Holy cow, look at the Russian hacking. So, this sort -- this group of democrats that have been so concerned about hacking over the last four weeks, now just released a guy that did gave one of the largest leaks to Assange in WikiLeaks in history. (Source: SPOK: Fox)
2.BWhile the 72-win mark is one of the headlines from his reign over the NBA, it takes a backseat to the six rings in any Jordan discussions. This group of Warriors only has the one championship together from last season and surely sees adding to that total as a bigger priority than the wins record. . (Source: Bleacher Report))