Answer : 1. "1"
Explanation :

The will be used before Tea because – Here, we are talking about a particular tea, followed by a Relative Pronoun (which). The sentence can also be written as –

The tea I am drinking is hot (tea-definite) Look at the examples given below : The flowers in her garden are beautiful. (Definite – the ones in her garden)

The flowers (that) are in her  

↓

Rel.pro.

garden are beautiful.

The dog in the backyard is very cute. (Definite-the one in the backyard)

The dog (which) is in the backyard is very cute.

↓

Rel.pro.

Hence, the tea is the right usage.