Question

3 ].what tense should you use: Past    Simple  or Present  Perfect ?   Example: yesterday--Past  Simple . already--   ....................  ,  when-- ...................., yet- ................., last year-- .............., just-  .....................  ,  2 days ago-- .................  Divide these writers into 3 groups: Russian,British and American.[M.Twain  L,Tolstoy  A.Milne A. Pushkin R.Kipling. J. London  P. Travers]

Answer 1

already - Present Perfect,
when - Past Simple
yet - Present Perfect
last year - Past Simple
just - Present Perfect
2 days ago - Past Simple 

Russian writers: Leo Tolstoy, Alexander Pushkin 
British writers: Alan Milne, Rudyard Kipling, Pamela Travers
American writers: Mark Twain, Jack London