Which one of the following pairs of rivers and tributaries is not correctly matched?

Consider the following characteristics of a tropical cyclone :

1. A warm sea temperature of > 26$$^\circ$$C

2. High relative humidity of atmosphere at a height of > 700 m.

3. Atmosphere instability.

The above mentioned characteristics are associated with which one of the following cycles of its development?

The shortest day length that occurs in the Northern hemisphere is on

The Indian Railways have gone in for qualitative improvements since independence. Which of the following have taken place in recent years?

1. Gauge conversion

2. Track electrification

3. Automatic Signals

Select the correct answer using the codes given below.