—I wonder if you can go shopping with me together．

    —Sorry．I       a letter all the morning and haven’t finished it yet．

    A．am writing                           B．was writing

C．have written                         D．have been writing

―I wonder if you can go shopping with me together．

―Sorry．I       a letter all the morning and haven’t finished it yet．

A．am writing                                              B．was writing

C．have written                                            D．have been writing