GMAT Test Prep: SC-80635487 GMAT Sentence Correction | TOEFL IELTS GMAT GRE SAT ACT PTE ESL

A a source of income without which most commercial airlines could not survive, are

B a source of income without which most commercial airlines could not survive, is

C and most commercial airlines use it as a source of income to survive with, are

D which is a source of income which is needed by most commercial airlines who could not survive without it, are

E which most commercial airlines use as a source of income without which they are unable to survive, is