Q. What are the conditions for dehydration of alcohols?

1. Concentrated hydrochloric acid as dehydrating agent and temperature at 180 degrees Celsius
2. Concentrated sulfuric acid as dehydrating agent and pressure at 18 atm
3. Concentrated sulfuric acid as dehydrating agent and temperature at 180 degrees Celsius
4. Concentrated carboxylic acid as dehydrating agent and temperature at 180 degrees Celsius