beat/ win/ defeat
Ⅰ. beat 打赢战胜。用于比赛时，后接宾语是战胜对手，表示赢了某人。如：
① Li Lei beat all the runners in the 100-metre race.
李磊在百米赛跑中赢了所有的对手。
② We are sure to beat them.
我们肯定会赢他们。
Ⅱ. win 赢得；获胜， 用作及物动词，后接宾语是表示某种比赛的名词或战争，而不是参加比赛的'对手。如：
① We won the basketball game.
我们赢得了篮球赛。
② Who won the race?
谁赢得了赛跑？
Ⅲ. defeat 战胜；赢得与win 一样，较正式，后接宾语时与beat一样，是表示人或代表群体的名词或代词，间或接表事物的名词或代词。 如：
Our class defeated / beat theirs in the basket-ball match yesterday.
昨天我们班在篮球赛中赢了他们班。
because/ because of
Ⅰ. because 是连词，后接句子， 是主句的直接原因，常用来回答由why 引导的特殊疑问句。如：
① Because he is ill, he is not here today.
因为他病了，所以今天没来。
② --Why are you in a hurry?
