The word “diligent” means “having or showing care and conscientiousness in one's work or duties.” For example: "after diligent searching, he found a parcel"

Option D: “Industrious” means “diligent and hard-working.” For example: "an industrious people striving to make their country prosperous" This is closest to the meaning of "diligent". Hence, this is the correct option.

Option A: “Intelligent” means “having or showing intelligence, especially of a high level.” For example: "Anna is intelligent and hard-working" This is a completely different meaning. Hence, this option is incorrect.

Option B: “Energetic” means “showing or involving great activity or vitality.” For example: "moderately energetic exercise" This is a completely different meaning. Hence, this option is incorrect.

Option C: “Modest” means “unassuming in the estimation of one's abilities or achievements.” For example: "he was a very modest man, refusing to take any credit for the enterprise" This is a completely different meaning. Hence, this option is incorrect.