Unsure of why "it" is considered a referential for question 1, and the video does not consider it. If we plugged in "keeping deep wounds free of bacteria" in the sentence, it would read "keeping deep wounds free of bacteria is difficult to keep deep wounds free of bacteria." I know "it" can function as a referential pronoun but it does not appear to be doing so here.

In question 5, can "but this is not a sustainable long-term solution" be considered a subsidiary conclusion? I know it isn't the main conclusion, but doesn't it both receive support from the first sentence and give support to the main conclusion/last sentence?