Final answer:
The correct answer is option 4. After the Tet Offensive, the mainstream American media openly criticized the war effort due to the reality of a stalemate and the disconnect between official claims and the actual situation on the ground.
Step-by-step explanation:
After the Tet Offensive in the Vietnam War, the mainstream American media began to openly criticize the war effort. This shift in media coverage was influenced by the coverage of the fighting in Vietnam, which highlighted the reality of a stalemate and the disconnect between official claims and the actual situation on the ground.
Walter Cronkite, a respected journalist, expressed concern about the war ending in a stalemate, further bolstering opposition to the war.