下各项词语中没有错别字的一项是( )

Playing the violin well is not ____ so easy as you imagined, dear! You must get fully prepared against anydifficulties, I say [ ]

The scientists are studying the effects of human activities______the environment

Mr. Richard hasn’t got any time to play golf these days, because he is ______ in the research of bird language.

The place was flooded ________ it had beenraining for several weeks