请认真阅读下面短文，从短文所给的A、B、C、D四个选项中，选出最佳选项。
Raynor Winn and her husband Moth became homeless due to their wrong investment. Their savings had been 1 to pay lawyers' fees. To make matters worse, Moth was diagnosed（诊断）with a 2 disease. There was no 3, only pain relief.
Failing to find any other way out, they decided to make a 4 journey, as they caught sight of an old hikers'（徒步旅行者）guide.
This was a long journey of unaccustomed hardship and 5 recovery. When leaving home, Raynor and Moth had just ￡320 in the bank. They planned to keep the 6 low by living on boiled noodles, with the7hamburger shop treat.
Wild camping is 8 in England. To avoid being caught, the Winns had to get their tent up 9and packed it away early in the morning. The Winns soon discovered that daily hiking in their 50s is a lot 10 than they remember it was in their 20s. Raynor 11 all over and desired a bath. Moth, meanwhile, after an initial 12, found his symptoms were strangely 13 by their daily tiring journey.
14, the couple found that their bodies turned for the better, with re-found strong muscles that they thought had 15 forever. "Our hair was fried and falling out, nails broken, clothes 16 to a thread, but we were alive."
During the journey, Raynor began a career as a nature writer. She writes, "17 had taken every material thing from me and left me torn bare, an empty page at the end of a(n) 18 written book. It had also given me a 19, either to leave that page 20 or to keep writing the story with hope. I chose hope."
功率较小，功率大小可通过电位器调节；档位
功率为最大值且不可调节。
，功率可从100W调节到400W，请按上述要求计算出满足要求的电热丝R1的阻值和电位器的最大电阻值R3。
，请计算处于这个档位时流过电阻丝R2的电流的变化范围。