Answer:
Imprisoning and executing hundreds of Buddhists.
Step-by-step explanation:
Ngo Dinh Diem was the Political leader and President of Vietnam. He ruled Vietnam with dictorial power. During his reign in South Vietnam, many Buddhist leaders and followers.
In 1963, under the Presidency of Diem, South Vietnam witness imprisonment and execution of many Buddhists leaders and followers, which later was named 'Buddhist crisis.' This crisis ignited protests from Buddhists.
The then US President Kennedy tried to impose Diem to take actions against Buddhist Crisis, which he ignored and instead he imposed martial law to stop Buddhist protesters. Diem's action of imprisoning and executing of Buddhists and those who opposed his reign made the US government to withdraw its support.
So, from the given options, the correct one is 'imprisoning and executing hundreds of Buddhists.'