He put 12 stamps in his collection.
Examples of this are:
2 and 
2 and 
4 and 
I'm guessing you have a work sheet going along with this which has actual images of containers. I've attached an example - if you can post the actual work sheet you're referring to I can edit this answer to correctly reflect your specific question.
Answer:
Answer is C
Step-by-step explanation:
hope you have s good day
<em>Look</em><em> </em><em>at</em><em> </em><em>the</em><em> </em><em>attached</em><em> </em><em>picture</em>
<em>Hope</em><em> </em><em>it</em><em> </em><em>will</em><em> </em><em>help</em><em> </em><em>you</em><em>.</em><em>.</em><em>.</em><em>.</em>
<em>Good</em><em> </em><em>luck</em><em> </em><em>on</em><em> </em><em>your</em><em> </em><em>assignment</em>