PL HELP The Online Child

Parents should seriously think about the online life of their children. "Online life" refers to the activities people are involved in while using the Internet. Today's teenagers have grown up with technology and the Internet. They are becoming more knowledgeable about technology, sometimes more so than their parents.
These days, teenagers spend a lot of their time on the Internet using social networking sites. Other times, teenagers enjoy spending time with their school friends or playing sports. Social networking sites provide the perfect place for teenagers to exercise their freedom. In addition, these teenagers also find a venue to express themselves openly with their online friends. They post pictures of themselves and share thoughts for the whole world to see. The problem is that the teenagers are not always aware that their images and words on the Internet are permanent.
Teenagers may not be aware that people often use fake identities on the Internet and give false information. In addition, problems with "friends" on the Internet can have real-life consequences. And just like a real child, the online child needs the parents to tell him or her how the world (of the Internet) works. The teenagers need to learn critical-thinking skills applicable to real life and Internet life.
While educating their children on the risks of the Internet, parents should also demonstrate trust and allow their children enough space to learn on their own. For example, parents can let their children know that they will be making frequent checkups on their children's social networking page. That way, children can learn to practice caution when they post content on the Internet, while still retaining a feeling of independence. Parents can take the check-up time to teach their children about safe online habits.

Which sentence could be added to the end of the introduction to strengthen it?
A.
However, these teenagers do not always use the Internet wisely.
B.
In effect, the lack of communication skills affects relationships.
C.
Teenagers are also one of the top consumers of new products.
D.
Throughout the world, Internet use has increased dramatically.