Since we are at risk of not delivering the required functionality on time, ………. :

“The last option should be chosen as it is the safest.”

• This sentence is clear and grammatically correct. It uses passive voice, which is acceptable but less direct than active voice.

“We should choose the last option as it is known to be the safest choice.”

• This sentence is also clear and grammatically correct. However, “it is known to be” is slightly less direct than “we know.”

“We should choose the last option as we know it is the safest choice.”

• This sentence uses active voice, making it direct and clear. It indicates that the decision is based on the team’s knowledge, which adds a sense of certainty and authority.

Overall, the third option is preferred because it communicates the information in a direct, clear, and confident manner.