(1)A puddle of dark liquid under a car indicates a leak in the oil or transmission fluid. (2)Another warning sign of car trouble is uneven wear on tire treads (3)If the outer edge of the tire tread wears out before the center, the tire is under- inflated. (4)The most significant early warning signal, however, is less and less mileage per gallon (5)Lower fuel economy is caused by a variety of problems ranging from a clogged filter to ignition or carburetor trouble The sentence that best expresses the implied main idea is:_______.
a. Several warning signs can indicate car problems.
b. A puddle of dark liquid under a car is a sign that a car has an oil or transmission-fluid leak.
c. The most significant warning signal of a car problem is getting lower mileage per gallon of gas.
d. Various problems may cause a car's fuel economy to decrease.

The entire statement can be summarised under a topic talking about how there are several warning signs for when a car is experiencing problems because it talks about these various warning signs and what they mean.

These signs are very important to note as they will help the car last longer. Signs such as a puddle of dark liquid under the car and lower mileage per gallon should be especially paid attention to.