fill in the blanks with the correct tense forms
a) your friends -- (wait) for you for over an hour. where -- you -- (be) all this time? you --(be) out for almost four hours.
b) she says that she -- (send) the letter a month ago; but, so far, she -- (not receive) any reply. she -- (thin) that her letter -- (be) lost in the post.
a) has been waiting; have you been; have been out
b) had sent; has not received; thinks; is
b) had sent; has not received; thinks; is