Explanation:

A tropical depression is a tropical cyclone, but a tropical cyclone is not necessarily a tropical depression. Confused? It is not that complex.
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain or squalls.
A tropical depression is the weakest form of a tropical cyclone with winds less than 39mph. When it reaches that speed it is then called tropical storm and given a name. As wind speeds increase it may become a hurricane or typhoon (depending on location). Hence option 4th is correct.