题目选项分析

Thanks to advances in science and technology, many people who might once have been crippled in childhood by diseases such as poliomyelitis or Charcot-Marie-Tooth disease now enjoy near-normal lifestyles.

Thanks to advances in science and technology, many people who, when they were children, might at one time have been crippled by diseases such as poliomyelitis or Charcot-Marie-Tooth disease now enjoy near-normal lifestyles.