Final answer:
The correct answer to the riddle is Chewing gum, which is hard when it starts being chewed, then becomes soft and can be blown into a bubble.
Step-by-step explanation:
The question relates to a riddle that requires logical reasoning to solve. The riddle describes something that is hard when it goes in, but soft when it comes out, and it gets harder when you blow it. Considering the options provided, the correct answer is C. Chewing gum, which fits the description perfectly. When chewing gum is initially chewed, it is hard; as it is chewed, it becomes soft; and if someone blows into the chewed gum, it can form a bubble which hardens as it gets bigger.