What happened in 2014 that made the ongoing civil war in Syria even more complicated?

A: the Arab spring led to demonstrations in Syria.

B: the Assad government used chemical weapons.

C: ISIS launched an attack on Syria.”””

D: The United States attacked a Syrian air base.”””

I am stuck between C and D pls help

5 answers

https://www.google.com/search?q=war+in+syria+2014&oq=war+in+syria+2014&aqs=chrome..69i57j69i60l2.6529j0j7&sourceid=chrome&ie=UTF-8

Read widely, and let us know what you decide.
??? what are the answers ???
It's A.
no i swear its c i got a 100
Is it a or c