Answer: Marley increased her goal to one million books because she was thrilled about her success and felt encouraged about her mission.
Step-by-step explanation:
her goal to 1 million - since it says increased, what else could work? her success could, but remember, it says books after, you can't say "Marely increased her success books," that just won't work.
was thrilled - after it, was her success. it could be felt encouraged, but personally I think "was thrilled" makes more sense here.
her success - she "was thrilled" about _____. You can't put "felt encouraged," and everything else is taken, besides this, so it's the answer!
felt encouraged - everything else is taken; it could be "was thrilled," but I feel like it would make more sense before "her success"