The correct answer is option D, Unusually warm ocean temperatures
El Nino causes the temperature of oceans to rise by a few degrees Celsius. Its major impact is felt in the pacific ocean where the winds that push deeper water to replace water pushed west gets weak. Due to weakening of wind effects the warm water gets piled up in east and not enough cold water is pulled in the upward direction. This makes pacific warmer in the eastern side. This is a hallmark impact of El Nino
