Final answer:
The term 'upheaval' corresponds to '(a) commotion' as it signifies a substantial or violent disruption, which 'commotion' also implies.
Step-by-step explanation:
The word upheaval matches with option (a) commotion. The word 'upheaval' refers to a strong or violent change or disruption, often in a political, social, or natural context.
Options (b) stillness, (c) harmony, and (d) stagnation all suggest a state of inactivity or lack of change, which are the opposite of what 'upheaval' conveys.
Therefore, commotion, which implies a state of confused and noisy disturbance, is the correct match for the word 'upheaval'.