Tom is afraid-------speak Chinese in public,because he is af

to；of
be afraid to do sth.真正的意思是“害怕做某事”,也就是主语对做某事内心感到恐惧；be afraid of doing sth.表示主语内心里不情愿做某事,也可以说是不希望发生某事,但自己不一定能避免它.
Tom is afraid to speak Chinese in publicbecause he is afraid of making mistakes,是指Tom害怕在公众面前说汉语（在公众面前说汉语会恐惧）,是因为害怕犯错（不愿意犯错）.