HOTSPOT
You create a custom style by using CSS3.
A box with rounded corners must appear around text. The box must match the following
illustration:
You need to add the CSS3 markup to your style.
How should you complete the relevant CSS styles? (To answer, select the appropriate
option from each drop-down list in the answer area.)
Answer: 
Explanation:
why do we need use border-box?
Correct answer is:
display: inline
border-radius: 10px
see https://jsfiddle.net/6vs4kzob/
This is not an exact result projection as you can see in illustration above.
Your inline option is showing border around text, the box-sizing: border-box intents to create box for entire paragraph width.
Answer is correct.