C is the answer to this question. You will not be able to open the computer if you would not press the power button. Pressing CTRL+ALT+DELETE may allow you to restart a computer. This will also allow you to open the task manager if there are some things that did you would like to manage. You need to press start if you would like to access some applications and other software.
The start button will also allow you to access different things. When you click the Internet Explorer icon, this means that you can access the internet using this search engine site. Take note that there are other applications that you can use in order to access the internet.