36.A It was not until in my late thirties that I made this important discovery:giving-away makes life so much more exciting.强调句
37.C One discovery I made about giving-away is that it is almost impossible to give away anything in this world without getting something back,though the return often comes in an unexpected form.
38.B step in and make the suggestion to the storekeeper
39.A my name would have to go on a long waiting list
40.C I wrote the postmaster a note of appreciation 同义