По с по языку : 1.what have you done since you returned from the sea? -ответ ( по ) 2.what had you done before you helped your mother last night? -ответ ( по ) 3.how long have you been learning english? -ответ ( по ) 4.what were you doing before you met yout friend yedterday? -ответ ( по ) 5.what are you going to do after fishing the ninth form? -ответ ( по )