1. Which is the largest gulf ?

Answer: Gulf of Mexico

2. Which is Longest road tunnel in the World ?

Answer: Lærdal Tunnel (Norway - 24.51 kilometre)

3. Which is the largest Mosque in World ?

Answer: Masjid al Haram (Saudi Arabia)

4. Which is the longest Platform ?

Answer:

Gorakhpur railway station, Uttar Pradesh, India (1355.40 meters)

5. Which is Largest library in the world ?

Answer: United State Library of Congress, Washington D.C.

6. Which is smallest state by area of India ?

Answer: Goa

7. Which is highest dam in world ?

Answer:

Jinping-I Dam - 305 m (1,001 ft) in China on Yalong river.
Second Highest is Nurek Dam 300 m (980 ft) Tajikistan on Vakhsh river.