Directions: Choose the option which is grammatically correct and the best version of the underlined part.

While levels of NO₂ in Indian cities are lower than the West, concentration of the gas doubled or tripled during the last five years.

While levels of NO₂ in Indian cities are lower than the West,

While levels of NO₂ in Indian cities are lower than those in the West,

While levels of NO₂ in Indian cities are lower than in the West,

While Indian cities have quite low levels of NO₂ than the West,

While levels of NO₂ in Indian cities are lower than they are in the West,