Concept:The question tests which listed properties are true for semiconductor/solid-state devices like transistors.
Explanation:I. Small size — correct for solid-state devices.
II. Low power requirement — correct, they consume little power.
III. Not easily damaged by high temperature — incorrect, semiconductors are heat-sensitive and can be damaged by excessive heat.
IV. Highly durable — correct, solid-state devices are generally rugged and long-lasting.
Therefore, the valid properties are I, II, and IV only.
Answer:C. I, II and IV only