Answer:
Option D, Food chains are linear, while food webs are complex.
Step-by-step explanation:
A food chain is a linear organization in which the producer lies at the first stage followed by consumer organisms lying at primary, secondary and tertiary stages of food chain.
While in a food web, there can be several interlinked food chains or there can be an organism within the food web which is part of several food chains at an instance. Hence, the linearity of organization cannot be retained in case of food web thereby making it more complex than the food chain.
Hence, option D is correct.