The correct answer is - b) They will continue to grow because of plate collision.
The Himalayan Mountain Range has been formed by the collision of the Indian and Eurasian tectonic plates. This process of collision continues in the present, and if it continues in the future, the end result will be a mountain range that is still growing in height because of the collision of the two tectonic plates. At the present, we have an estimated annual growth in height around 8 cm, in the future this number should slowly start to become smaller and smaller, but still it will contribute to an even higher mountain range than what we know today.