Explanation:

 The prime cause of monsoon is unequal heating between the landmass and surrounding ocean. Due to rising Oceanic temperatures on account of global warming the temperature gradient between land and sea is getting disturbed and it has potential to adversely affect monsoons.
El Nino Southern Oscillation or ENSO is known to cause unusual warming of eastern pacific thereby disturbing the heat gradient between eastern and western pacific and adversely affecting monsoons.
Third is incorrect because positive Indian Ocean dipole has positive effect on Indian monsoon as it brings rainfall.
During the Positive IOD, the eastern equatorial Indian Ocean off Sumatra in Indonesia becomes colder than normal while the western tropical part of the Indian Ocean near the African coast becomes unusually warm. Such an event has been found to be beneficial for the monsoon.