Final answer:
The term 'cad/cid' means to fall or to happen by chance, therefore the correct answer is 3) both a and b. It is present in words like 'accident' and 'cascade'.
Step-by-step explanation:
The term 'cad/cid' originates from Latin, and it refers to the concepts of falling or happening by chance. Therefore, when we are faced with the options provided, the correct answer is 3) both a and b. The root 'cad/cid' appears in various English words that carry the meaning of falling or occurring unexpectedly, such as 'accident' (something that happens by chance) or 'cascade' (a waterfall or series of small waterfalls, suggesting the idea of falling).