Most pure oils are odorless and light yellow (colorless).

The blending of essential oils should be conducted by professional aromatherapists.

He is busy ______ the bicycle. A: oil B: oils C: oiling D: oilling

The development of oils （） the increasing demands made by the steady rise in powers produced by modem diesels.

Liquid fats are commonly referred to as（ ）. A: lipids B: fats C: oils D: waxes

In large marine diesel engines cylinder oils usually contain additives formulated to impart the （） to clean the rings and grooves.

Chinese traditional painting, also known as “Guohua”, is different from Western painting because oils are used in it.

Which one is NOT the obtaining method for essential oils? A: Pressing B: Organic solvent extraction C: Hydrodistillation D: Hydrodiffusion

该句逗号是否使用正确：One of the main challenges encountered by the refining industry worldwide, is the deterioration in feedstock quality and the introduction of heavy crude oils.

Emulsion oils and sodium nitrite are both approved additives， but the latter cannot be used if any pipes are （） or if any soldered joints exit.