I think I'll go with C.
A is eliminated because of 'were' ascended.Itz not right.
B has baloon in the first part of sentence and then again has a reference in the second part.
C has that and appears correct.
D - 'to ascend' sounds correct. But position of 'that' is not right for me.
E.'ascending' -Incorrect tense.
510 on my first GMAT. 610 on second GMAT.!
The struggle continues.