Which of the following acts as a stimulus in the process of hydrotropism?

The stimulus in the process of thigmotropism is:

A growing seedling is kept in a dark room. A burning candle is placed near it for a few days. The top part of seedling bends towards the burning candle. This is an example of:

The growth movement of a plant part in response to the touch of an object is called:

The climbing organs of plants like tendrils grow towards any support which they happen to touch and wind around the support. This is an example of: