Bob often__________ his __________ after supper.

选词填空。

    Vienna，both the capital city of Austria and the centre of____classical music．is a beautiful old city on the River Danube．In the eighteenth century,lots of____came to study and work there．Among them，three composers____Johann Strauss(the father and the son)and Mozart were very famous．Mozart could play the piano and the violin before six．His family____him around Europe to give concerts and he wrote____of pieces of music．

生物进化的总体趋势是由____，由____，由____．