Answer : 1. "but"
Explanation :

• The conjunction “but” will be applied in this sentence.

• When linking things that share the same grammatical type of coordinating conjunction, we employ the word “but.”

• The conjunction “but” joins concepts that contradict.

Example: I love fruits but I am allergic to dragonfruit.

They’ve bought a house in Mumbai but they still haven’t sold their house in Delhi.

• As we can see, the sentence is linking two phrases that are in contrast, thus,

the conjunction “but” is appropriate for this sentence.

• Therefore, the complete sentence is: A heavy storm was forecast but the weather was clear