$17.$ Aviation gasoline is characterized by:

a$)$ Low octane rating

b$)$ High lead content

c$)$ Low vapor pressure

d$)$ High sulfur content

$18.$ Kerosene is commonly used as:

a$)$ Jet fuel

b$)$ Diesel fuel

c$)$ Heating oil

d$)$ Lubricating oil

$19.$ Diesel oil is characterized by:

a$)$ Low viscosity

b$)$ High cetane number

c$)$ Low sulfur content

d$)$ High vapor pressure

$20.$ Gas oil is mainly used for:

a$)$ Cooking

b$)$ Heating

c$)$ Lubrication

d$)$ Lighting