The correct answer is C) Colorless liquid, faint odor. According to the Chemical Data Guide published by the US Coast Guard, 1,3-pentadiene is a colorless liquid with a faint odor. This information is consistent with the characteristics listed in answer choice C. The other answer choices are incorrect because they do not accurately describe the properties of 1,3-pentadiene as specified in the Chemical Data Guide. For example, option A describes a pale yellow liquid with a strong odor, which does not match the guide's description. Similarly, options B and D provide inaccurate details about the color and odor of this chemical.