Перепишите след. предложения; подчеркните в каждом из них глагол-сказуемое и определите его видо-временную форму и залог. a) 1. Today scientists are still looking for the substance as a source of energy. 2. The Mendeleyev system has served for almost 100 years as a key to discovering new elements. б) Synthetic rubber products were developed between 1914 and the 1930s. 2. The intensity of this process is influenced by many factors.

Шестое, Пятнадцатое, Двадцать первое и Семнадцатое