Sine qua non a) take notice b) a prerequisite; absolutely ...

[madam-professor]

sine qua non
 
  a) take notice
  b) a prerequisite; absolutely essential
  c) someone who is unacceptable or unwelcome
  d) a conclusion that does not follow from the evidence

Question 2

mea culpa
 
  a) in good faith
  b) let the buyer beware
  c) formal admission of guilt or responsibility
  d) after death or following a difficult experience

[vkodali]

Answer to Question 1

b

Answer to Question 2

c

[madam-professor]

Great answer, keep it coming

[Dinolord]

Thanks for the timely response, appreciate it