Now i have understood.....Thankyou so much

In 2001, the Peruvian government restricted number of tourists to 500 and started giving expensive permits to hike the remote Inca Trail.

Before 2001 daily visitors to the trail numbered in the thousands.

Claim: This permit program has successfully prevented deterioration of archaeological treasures along the Inca Trail.

We need to strengthen the claim.

(A) Since 2001, tourist guides along the Inca Trail have received 50% to 100% increases in take-home pay.

Irrelevant.

(B) Villages near Machu Picchu have experienced declines in income, as fewer tourists buy fewer craft goods and refreshments.

Irrelevant. The point is whether the deterioration of archaeological treasures has been prevented.

(C) Many of the funds from the sale of Inca Trail permits are used to staff a museum of Incan culture in Lima, Peru's capital, and to hire guards for archaeological sites without permit programs.

Irrelevant how the money is used for things besides the Inca trail.

(D) Since 2001, Incan ruins similar to Machu Picchu but not on the Inca Trail have disintegrated at a significantly greater rate than those on the Inca Trail.

Correct. You are given that the other "similar" ruins have disintegrated at a far greater rate. That means the actions taken to preserve the Inca trail are working.
The use of the word "similar" is enough to say that the Inca trail and others are comparable.

(E) The total number of tourists in Peru has risen substantially since 2001, even as the number of tourists hiking the Inca Trail has remained constant.

Total number of tourists in Peru is irrelevant. We know that before 2001, thousands of people were visiting the Inca trail. Now only 500 are visiting every day. So deterioration has been prevented.
How many people actually visited Peru before and now is irrelevant.

Answer (D)