Which of the following is true about biofuels? a. They are made from plant materials and animal fats. b. They are made by directly harnessing energy from the sun. c. They use energy from water. d. They use energy from the Earth’s core.

Answer is option A.

They are made from plant materials and animal fats.

Explanation:

The fuels produced directly or indirectly from biomass (organic material) which contains plant or algae materials such as grass, wood, charcoal, agricultural wastes, crops, etc and animal waste such as animal dung are known as biofuels. Solid, liquid and gaseous biofuels are available.

In primary biofuels, an unprocessed form of organic materials is used. They are used for cooking, heating, electricity production, etc. Examples include fuelwood, pellets, wood chips, etc.

In secondary biofuels, processed forms of biomass or organic materials are used. They are used in vehicles and industrial processes. Examples include liquid biofuels such as biodiesel and ethanol.  Biodiesel is produced by combining alcohol with vegetable oil or animal fat. Ethanol is a type of alcohol produced from biomass containing sugar or starch (sugar cane, sugar beet, wheat, corn, maize, etc) by using the processes of fermentation and distillation.

The liquid biofuels such as ethanol and biodiesel are referred to as first-generation biofuels. Second-generation biofuels refer to liquid fuels produced from the processing of certain components from plant matter such as cellulose, hemicellulose, and lignin.

Biofuel is a renewable energy source that can be replenished readily. It is very cost-effective and environmental friendly than fossil fuels such as natural gas, petroleum, coal, etc.

a

Explanation:

i just took the test. hope this helps !!

answer: zinc is the substance which has a volume of 1.38 .

density is defined as the mass of an object per unit volume.

it can be calculated by dividing mass of a substance by its volume i.e.

si unit of density is kg per cubic meter and cgs unit of the same is gram per cubic centimeter.

now from the given data volume can be calculated by the formula .

hence, the volume of aluminium will be = which comes out to be 1.703 .

similarly, volume of zinc, chromium, and nickel will be 1.378 , 0.869 , and 0.356 respectively.