Explanation:

- "The rumours usually spreading like wild fire."

- Incorrect because "spreading" is not in the right tense for this structure. It would require a helping verb, such as "are."

- "The rumours usually spread like wild fire."

- Correct. "Spread" is simple present tense, which is appropriate for this context to describe a regular action.

- "The rumours usually spreads like wild fire."

- Incorrect because "spreads" is singular, while "rumours" is plural, so they don't match in number.

- "The rumours usually are spreading like wild fire."

- Incorrect in this context. It suggests ongoing action, not habitual action, which "usually" implies.