"why is petroleum the primary fuel used for transportation in the united states? i. it has a high energy value per unit volume. ii. it has quick start and stop times for providing energy. iii. it produces a low amount of pollution per joule."

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.