Sasha wants to be chairman. He is a doctor vs. He works as a doctor. In written Russian, on the other hand, there are various ways of expressing the present tense of 'be', the most important of which is the verb , which, like most linking verbs, governs the Instrumental case. Baikal is the deepest lake in the world.
Problems having to do with an atomic reactor accident are very serious.
Some verbs, not in themselves linking verbs, take two objects which have a linking relationship. Note that the English linking verb 'to be' can be inserted between the two objects. In the corresponding Russian sentences the objects are Accusative and Instrumental, respectively. In the following examples is the Instrumental of and is the Instrumental of 'head'. . They elected Sasha chairman. .