Write a multi-choice question for the following article, with the given choices and answer: Article: One of the most famous scientists to study adaptations was Charles Darwin . He was born in England in 1809. He wasn't the best student in his school, but when he was 16, his father sent him to a medical school. Charles liked spending time outdoors observing nature more than having medical classes. He dropped out without graduating. Next, Charles' father sent him to school to become a minister . This time he made it to graduation, but he didn't want to do the work of a minister. His friends encouraged him to follow his interest in science. Luckily, Charles was invited to sail on the Beagle as an unpaid scientist after graduation. The Beagle was to travel to South America and then around the world. Their task was to make maps of the places they visited. On December 27th, 1831. Charles Darwin sailed from England on the Beagle. The trip was planned to last two years. In fact, it lasted five. During this time, he saw many amazing things. He collected lots of plants and animals and took them back to England to begin his scientific study. Twenty-three years later, Darwin published a scientific paper with another man named Wallace. Darwin described how some animals have adaptations that help them survive. _ are passed on to offspring . Darwin's ideas about adaptations are still very important to the study of living things. Options: A twenty B twenty-three C forty-five D fifty Answer: D fifty Question:
The answer to this question is:
When Darwin published the scientific paper, he was _ years old.