問問有關現在進行式既問題

Problematic sentence:
Tom is repeatedly throwing a ball at me. (not making sense)

Tom 不斷向我拋d球
~Tom repeatedly threw balls (or a ball) at me.
~Tom has repeatedly thrown balls at me.
~Tom has been throwing some balls at me.

現正向我拋球
Tom is (now) throwing a ball at me.

2015-03-25 00:44:56 補充：
Tom準備law 個球拋向我，宜家我講:

Tom is about to throw a ball at me.
Tom is going to throw a ball at me.

Tom is throwing a ball at me. (it is wrong to correctly decribe the present situation)

就如你所講:他一直在不斷地"在向你抛球"，所以用現在進行時態動詞ok啦。不過如你所寫"Tom is throwing balls at me"意思是他正在同時向你抛來"很多球"=好多個球一齊抛過來你處。
假如他每次只是抛一個球給你，則應該用單數
Tom is throwing a ball at me.
如果再清楚你表達你解釋那樣"tom是正在不斷地重復地抛一個球給你"
Tom is throwing a ball at me repeatedly.
或
Tom is repeatedly throwing a ball at me.

repeatedly是adverb形容throw這動作的副詞...就可以表達你描述的"情況"。
以上是tom那邊有很多球他不停地抛向你，但你接了卻沒有抛回去他那邊的。

假如你們是互相抛一個球...就是不同的寫法
Tom is throwing a ball at me back and forth.
便已經表達來來回回的互相抛球...因為己經back and forth已經形容throw的情況就不用repeatedly了。