Explanation:

- Option 1: go - This means to proceed or move to a location or state. Not commonly used in the sense of achieving a capacity or target.

- Option 2: off - This implies something going away or being inactive, which doesn't fit with reaching a production goal.

- Option 3: hit - This verb often denotes achieving or reaching a target, making it suitable for stating when full production capacity is achieved.

- Option 4: hitting - This is the present participle form of "hit," indicating they are in the process or about to achieve full production capacity.