The correct answer is 'so as not to' which is a proper idiom meaning 'in order to not'. 'I took a cab so as not to be late' is grammatically correct. Option B 'in order to not' is incorrect because 'not' should not be separated from 'to' - it should be 'in order not to'. Option C 'to avoid' would require 'being' after it ('to avoid being late'), not the bare infinitive 'be'. Option D has both grammatical errors ('wont' should be 'won't') and structural issues.