In Trust Games Where Amounts Sent by Senders Is Tripled

In trust games where amounts sent by Senders is tripled by the experimenter "trust does not pay" in the sense that on average returns to trustors is typically less than their initial endowments." One possibility for why this happens is that:

A) participants do not necessarily interpret the game in the same way; explaining the underlying strategic implications usually leads to higher returns from trust.
B) on average trustees return more than one-third of the amount received.
C) a certain amount of confusion needs to be allowed for; explaining the underlying strategic implications usually leads to even less trust.
D) on average trustees reject the trustor's offer, resulting in both players getting zero.