Hi
dadihungSplit 1: Much/manyCollective nouns (e.g: percentage, proportion, company, team, class, ...) are singular if the individuals act as a group (which is in most cases),
However, they are treated as plural only if the individuals are acting individually (e.g: The jury are arguing among themselves)
so
Much is our choice.
Split 2: Is last year correct?I am not 100% sure of my answer for this, but I think the relative pronoun "that" should not be omitted.
The rule I know says that the relative pronoun can be only omitted if its noun is an object of the verb of the sentence.
(e.g: The city (
that) he visited was wonderful) ---> the city is the object of the verb "visited"
in our example, "percentage" is the subject, so "that" shouldn't be omitted.
Please check this question, it is related to yours:
https://gmatclub.com/forum/exceeding-even-the-figures-predicted-by-the-most-optimistic-financial-53878.html