1. Which is smallest planet ?

Answer: Mercury

2. Which is the lightest gas ?

Answer: Hydrogen

3. Which is the longest Platform ?

Answer:

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

4. Which is the smallest state of India by Population ?

Answer: Sikkim

5. Which is Largest railway route in India ?

Answer: Dibrugarh in Assam to Kannyakumari in Tamil Nadu.

6. 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.

7. Which is the Densest populated State of India ?

Answer: West Bengal