Find out which underlined part of the sentence below has an error and mark the option accordingly. Butterflies are considered as the main agent of transferring pollen grains. Sometimes, this gives rise to different species of flowers, a true fascination unknown to the science world.

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Dogs, often hailed as humans’ best friends, have been the topic of many scientific studies looking into how they might boost our well-being. It is likely that humans and dogs have shared a special bond of friendship and mutual support ever since at least the Neolithic period — but why has this bond been so long-lasting? A recent study showed that owning a dog reduces a person’s risk of premature death by up to a third. Also, researchers at the University of Harvard in Cambridge, MA, suggest that dog owners have a lower risk of heart disease.Dogs can strengthen our health not just as we grow older, but also much, much earlier than that: before we are even born. Research published last year suggests that children who were exposed to dogs while still in the womb — as their mothers spent time around dogs during pregnancy — had a lower risk of developing eczema in early childhood. When we interact with dogs, our oxytocin levels shoot up. Since this is the hormone largely responsible for social bonding, this hormonal “love injection” boosts our psychological well-being. Previous studies analyzed in the review have revealed that dog owners have more positive social interactions, and that the presence of canine friends makes people more trusting. Moreover, dogs appear to reduce symptoms of depression and render people more resilient to stress. That is why dogs are often used as therapy animals.