Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

In the earliest times children got their education directly from parents and other adults. They learned mainly skills for survival. Adults passed down this knowledge through spoken language. Eventually cultures around the world began inventing writing. As societies developed theyset up schools to teach reading, writing, maths and other subjects.

The first schools were usually just for boys. Most of the students came from rich and powerful families. Often the purpose of their education was religious training. In many cultures the religious leaders formed the highest level of society. Some schools had other purposes as well. Many schools focused on military training. Sometimes youths attended special schools to learn the art of public speaking. These skills were meant to help them become future leaders.

Most girls received their education at home. They learned cooking, sewing and other useful skills. Over time education became available to more people, not just the rich and powerful. The governments of some countries set up public systems of education in the 1800s. More schools opened to girls.

During the 1900s marks, or grades, became a new measure of learning. Testing became a regular part of formal education. As education became more important to people, teachers' colleges opened. The requirements for becoming a teacher became stricter. Teaching became a highly respected profession.

The word “they” in the passage refers to________.