Question 1207392
.
<pre>

As the problem is worded, two answers are possible:


    (C) 60 days

and

    (D) 120 days.


To exclude two answers and allow only one, the problem's question should be posed differently.
It should ask about the  {{{highlight(highlight(minimum))}}}  number of days, when M and C will go to the grocery in the same day next time.
</pre>