Answer: 3. gravitropism
The movement of plants in response to stimuli is called as tropism. Plants respond to different stimuli like light (phototropism), water present in the soil (hydrotropism), gravity (gravitropism) and touch (thigmotropism).
Gravitropism refers the growth and movement of plant parts with respect to the force of gravity exerted by earth. The roots shows positive gravitational tropism because they are growing towards earth gravity. The shoots or stems shows negative gravitational tropism because they are moving or growing against the gravity.
B shield volcanoes is the correct answer!
Hodgkin's disease or hodgkin's lymphoma
In bone growth, the medullary cavity is enlarged because of the activity of osteoclasts. These are cells working to break down bone, resorbing old bones which will line in the medullary cavity. The cavity is also enlarge as the cells contribute to the increase in length and diameter of a growing bone.