The correct answer is B. The bird
In biology, a food chain refers to a type of network that describes the way organisms feed on others and are also eaten by other organisms, which creates different levels. In this, the first level is the producers that include plants or organism that can produce their food; primary consumers the that are herbivores and eat producers; then there are the secondary consumers that eat the herbivores; the tertiary consumers that eat the secondary consumers; the top predators and finally the decomposers. This implies in the case of the food chain presented, the fruit is the producer, the fly is the primary consumer, the spider is the secondary consumer and the bird is the tertiary consumer as this feeds on the secondary consumer.
regulation of gene expression. gene expression can be regulated by various cellular processes with the aim to control the amount and nature of the expressed genes. these regulatory proteins bind to dna and send signals that indirectly control the rate of gene expression