A can do a work in 17 days and B in 23 days. If they work on it together for 5…

Step 1: Find the 1-day work of A and B.
A's 1-day work = 1/17
B's 1-day work = 1/23

Step 2: Find their combined 1-day work.
(A + B)'s 1-day work = (1/17) + (1/23)
= (23 + 17) / (17 × 23)
= 40 / 391

Step 3: Calculate the total work done in 5 days.
Work done in 5 days = 5 × (40 / 391) = 200 / 391

Step 4: Find the fraction of work left.
Total work is always considered as 1.
Remaining work = 1 - (200 / 391)
= (391 - 200) / 391
= 191 / 391

Final Answer: Option A