Answer:
- Scientists reached a decision about when to begin the experiment.
Step-by-step explanation:
An Active voice is defined as the grammatical construction in which the subject itself performs the action and acts upon the verb.
The given sentence is in the passive voice as the subject i.e. 'Scientists' is receiving the action and being acted upon by the verb and thus, the object and action are emphasized in the sentence. In order to convert it into the active voice, the subject needs to perform the action that the verb states as mentioned in the above sentence so that it follows the pattern of 'subject(scientists) + verb(reached) + object(a decision).'