Answer:
A) World War II and the Vietnam War.
Step-by-step explanation:
John Steinbeck's essay "Symptoms" talks about the post- war effects that war has on soldiers. Steinbeck was a World War II correspondent working for the New York Herald Tribune and this essay was part of his work during that time.
Likewise, Tim O'Brien's "Ambush" talks of the speaker's experiences during the Vietnam War. It specifically talks of his encounters at the My Khe ambush site where the narrator, who was a soldier, saw his enemy blown off by a grenade. This chapter of "Ambush" was part of the collection of short stories "Things They Carried".
So, the answer to the question is both authors wrote about the World War II and the Vietnam War wars.