Заполните пропуск: she to be more polite and patient. a) must b) can c) ought d) should

dmitri mendeleev is a great russian scientist of the 19th century.he  is recognized as a great chemist who created the periodic classification of the elements.dmitri mendeleev was born in tobolsk in 1834. at school,dmiti  succeed  in mathematics,physics,and geography but was not good at languages.in 1855 he graduated from pedagogical institute in st peterburg with a gold medal for his achievements .in 1856,he received a degree in chemistry.dmitri mendeleev's contribution to the world's science was enormous. he was the first created the dependence of the qualities of the elements on their atomic weight.he forecast that the gaps in the table of elements would be filled in by elements whith  had not  been discovered yet.dmitri mendeleev was greatly honoured as a member of academies in many countries.elements no 101  was named after him.