题目内容：
根据以下内容，回答题。Passage Five
Looking back on my childhood, I am convinced that naturalists are born and not made. Although we were brought up in the same way, my brothers and sisters soon abandoned their pressed flowers and insects. Unlike them, I had no ear for music and languages. I was not an early reader and I could not do mental arithmetic.
Before World War I we spent our summer holidays in Hungary. I have only the dim memory of the house we lived in, of my room and my toys. Nor do I recall clearly the large family of grandparents, aunts., uncles and cousins who gathered next door. But I do have a crystalclear memory of the dogs, the farm animals, the local birds, and above all, the insects.
I am a naturalist, not a scientist. I have a strong love of the natural world and my enthusiasm had led me into varied investigations. I love discussing my favorite topics and enjoy burning the midnight oil while reading about other people's observations and discoveries. Then something happens that brings these observations together in my conscious mind. Suddenly you fancy you see the answer to the riddle, because it all seems to fit together. This has resulted in my publishing 300 papers, and books, which some might honour with the title of scientific research.
But curiosity, a keen eye, a good memory and enjoyment of the animal and plant world do not make a scientist: one the outstanding and essential qualities required is self-discipline, a quality I lack. A scientist requires not only self-discipline but hard training, determination and a goal. A scientist, up to a point, can be made. A naturalist is born. If you can combine the two, you get the best of both worlds.
The author can't remember his relatives clearly because__________. A．he was too young when he lived with them
B．he was fully occupied with observing nature.
C．he didn't live very long with them
D．the family was extremely large
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