Given the question: Read the following article and select the best answer. Article: Tigers are among the most admired and most feared animals in the world . When we think of a tiger, we think of danger. We think of the big teeth and large feet of it. We also think of beauty. The tiger is a hunter that hunts alone. In fact , tigers are probably better than any other land mammal at catching large animals without help. Even so, the life of this big-game hunter isn't easy. Finding food can be difficult, especially for a tiger that is old or weak. Most of the animals it tries to attack get away. A tiger sometimes goes weeks without eating. When that happens, it may hunt animals that can be dangerous even for a tiger. When they are in a bad situation, some tigers may even attack humans. But in fact, tigers kill very few people each year. Most tigers run away when they see people. What tigers have done to people can't compare to what people have done to tigers. Over the last 200 years, we have almost killed tigers in the wild . Today, the tiger is one of the most endangered animals on Earth. A tiger may live 20 years or more, if it is not disturbed by humans. Female tigers usually live longer than male tigers, because the males live more dangerously. It isn't easy for people to tell a male from a female unless the female happens to be with her babies.Only females take care of the young. The big difference between males and females is size. Male tigers are much bigger. Tigers are big eaters. In a single year, one tiger must eat about 70 deer or other large animals. That is one reason why tigers hunt alone. If they lived in big groups, they could never find enough animals to feed them all. Question: The easiest way to tell a male tiger from a female one is by looking at their _ - size - running speed - way of hunting - claws
The answer is:
size