The correct option is A sharp
The most apt word that has same meaning as the italicized word in both sentences is Option A, 'Sharp'. Sharp is used for a person who is intelligent or quick to notice things. It also means clear to understand. The context of sentence I is that Sam is very sharp so he is able to get out of tight spots often. Sentence II means that the difference between the two tasks was quite clear. Option B, 'clear' means understandable. Option C 'intelligible' also means understandable. Option D 'visible' means able to be seen. Thus, B, C and D are incorrect options and correct answer is option A, 'sharp'.