题目选项分析

The physical structure of the human eye enables it to sense light of wavelengths up to 0.0005 millimeters; infrared radiation, however, is invisible because its wavelength - 0.1 millimeters - is too long to be registered by the eye.

The physical structure of the human eye enables it to sense light of wavelengths up to 0.0005 millimeters; however infrared radiation has a wavelength of 0.1 millimeters that is too long for the eye to register, thus making it invisible.