Fill in the blank with the best word to complete the following sentence:

"It was raining ____ so I decided to stay inside."
"It was raining heavily so I decided to stay inside."
Complete the following task based on the instruction and optional input provided.### Instruction:
Fill in the blank with the best word to complete the following sentence:

"It was raining ____ so I decided to stay inside."

### Output:
"It was raining heavily so I decided to stay inside."