Answer:
b. nettop
Explanation:
Since in the question it is said that helen want to buy a new computer so that she can follow her friends and family through social media and can communicated with them through email.
So, in this given scenario, the most appropriate option is nettop as it is cheap plus it also consume less power and it is small in size i.e it is easy to carry product. The use of this facilitates into the web browsing , processing of document, etc
Hence, b option is correct