基礎英文文法 the / are / a

他們正在看電視
They are watching TV那句正確
因為TV前面甚麼the /a都沒有

The & a的運用
a是在第一次描述那些事物時運用的
the是再描述之前已提及過的事物時運用的

For examples:
A boy is reading a book.The book is written by Paul Chan.
A computer is sold in a shop.The computer is expensive.


Hope this can help you!!

they are watching TV.Is 正確.