Correct Answer: D. architect

Correct Answer: C. 5

Correct Answer: B. Joel

Correct Answer: B. decreasing the activation energy of the reaction

Correct Answer: C. 3,500kg

Correct Answer: C. an increase in the average speed of the gas molecules

Correct Answer: D. Umar

Correct Answer: C. incomplete combustion of petrol

Explanation

The deposition of carbon (often seen as soot) in the exhaust pipe of cars is a direct result of the combustion process. Let's analyze the options:

• A. presence of carbon in petrol: Petrol is a hydrocarbon, meaning it contains carbon. While true, this statement alone doesn't explain *why* it's deposited. If combustion were complete, the carbon would be converted to carbon dioxide (a gas), not solid carbon.

• B. dehydrogenation of petrol: Dehydrogenation is the removal of hydrogen atoms. While complex chemical reactions occur, dehydrogenation is not the primary mechanism leading to solid carbon deposition in the exhaust pipe.

• C. incomplete combustion of petrol: This is the most accurate explanation. When petrol (a hydrocarbon) burns with an insufficient supply of oxygen, it undergoes incomplete combustion. Instead of producing only carbon dioxide (CO2) and water (H2O), it also produces carbon monoxide (CO) and/or solid carbon (C), commonly known as soot. This solid carbon is what gets deposited in the exhaust system.

• D. presence of additives in petrol: While petrol does contain various additives, and some might contribute to other types of deposits, the primary source of the significant *carbon* deposition (soot) is the incomplete burning of the main fuel itself, not typically the additives. Additives are often designed to *prevent* deposits or improve combustion.

Therefore, the most direct and correct reason for carbon deposition in the exhaust pipe is the incomplete combustion of petrol.

The final answer is C

Correct Answer: C. Be Constant

Explanation

According to Newton's Second Law of Motion, the net force acting on a particle is equal to the rate of change of its linear momentum:

F_{net} = \frac{dp}{dt}

Where:

• F_{net} is the total (net) force

• p is the linear momentum

• t is time

If the total force acting on the particle is zero (F_{net} = 0), then:

0 = \frac{dp}{dt}

This means that the rate of change of linear momentum with respect to time is zero. If a quantity's rate of change is zero, it means the quantity itself is not changing; it remains constant.

Therefore, the linear momentum will be constant.

The correct answer is C. Be Constant

Correct Answer: D. Reducing the risk of crop failure

Explanation

The primary purpose of mixed cropping in agriculture is to reduce the risk of crop failure. Mixed cropping involves growing two or more different crops together in the same field. This practice helps farmers mitigate the potential negative impacts of pests, diseases, adverse weather conditions, and market fluctuations that can affect a single crop.