In the 20th century, children's education started to seem like adult work. The structure of the curriculum and the activities became more structured. In addition to 6 hours of school, students were often required to work on 2 hours of ______ each day as well.

a. Artwork
b. Music practice
c. Sports
d. Homework

d. Homework

To answer this question, we need to understand the context of children's education in the 20th century. During this time, there was a shift towards more structured and formal education for children. Along with the typical six hours of school, students were often required to work on additional activities outside of school hours.

Now, let's consider the options:

a. Artwork: While art is an important part of education, it might not necessarily be the activity that students were required to work on for an additional two hours.

b. Music practice: Music education has always been a significant component of children's education, and many students are required to practice their musical instruments or vocals outside of regular school hours. This option seems plausible.

c. Sports: Sports and physical education are also essential aspects of a well-rounded education. However, it may not necessarily require an additional two hours of work outside of school.

d. Homework: Homework is a common practice in education, where students are given assignments to complete at home. It is likely that students in the 20th century were required to spend an additional two hours on homework each day.

Given the context and the options provided, the most likely answer is d. Homework.