Answer:
One event that causes tension is when the sergeant-major says, "I don't know what the first two were, but the third was for death."
This statement causes tension because the audience does not know why this man wished for death. Since the reader does not know what the first 2 wishes were, it makes the reader wonder what could be so bad that the man wanted to die. It creates tension because now the reader is worried about what other people might wish for. Additionally, the reader is concerned about how these wishes might affect the people at dinner. If one man could ruin his life with just 2 wishes, it is possible for the new characters to do the same.
This uncertainty and fear are what create the majority of the tension.