سوال ۳ کنکور ارشد علوم کامپیوتر ۱۳۹۸

The clue is that the niece can imagine a tree and a stick as a castle and a wand and play for hours in a fairy kingdom — this describes a strong, lively, richly detailed imagination. vivid means producing powerful, clear, lifelike images in the mind, so a "vivid imagination" is the standard collocation that fits. The others do not: vacuous = empty, lacking ideas (the opposite of what is described); cyclical = recurring in cycles (unrelated to imagination); careless = negligent, not paying attention (does not describe creativity).