2 hard writing questions

in addition to being a good source of protein and calcium, (yogurt contains bacteria that are good for and) beneficial to the human immune system.

the answer is (yogurt contains bacteria that are) i dont understand why in the answer there is “are” because bacteria is singular.

  1. the harsh conditions in which bristlecone pine trees live may help to explain their exeptional longevity, (because those same conditions are also inhospitable to) the pests that can attack the trees.

i didn’t understand why its correct. if i start a new clause with a comma i should start with “for” and not “because”. i disqualified the answers with “because” immediately

Bacteria is plural. Bacterium is singular.

ahh… thank u very much