Which of the following is not likely to cause Tsunami?

Tsunami is a natural phenomenon in which sea waves are produced due to the disturbance under the sea.

i. A major nuclear explosion under sea, earthquake or volcanic eruption can cause tsunami.

ii. Lightning is another thing. It is caused by the accumulation of charges in clouds.

iii. Negative and positive charges meet which produces streaks of bright light.

iv. We see streaks as lightning.