Выполните: IV. Open the brackets putting the verb in the right tense. Dear Mary, I...just(receive) your letter and now I (write) to you. I am very busy preparing for my exams. It is 9p.m. now and I (sit) at my desk. I l(sit) here since 11a.m. I (do/not) all the exercises yet. Thank you for everything you have done for me. I hope to hear from you soon. Yours, Helen.