题目选项分析

Rainwater contains hydrogen of a heavy form called deuterium. The deuterium content of wood reflects the deuterium content of rainwater available to trees during their growth. Wood from trees that grew between 16,000 and 24,000 years ago in North America contains significantly more deuterium than wood trees growing today. But water trapped in several North American caves that formed during that same early period contains significantly less deuterium than rainwater in North America today.

Which of the following, if true, most helps to reconcile the two findings?

【选项】Trees draw on shallow groundwater from rain that falls during their growth, whereas water trapped in caves may have fallen as rainwater thousands of years before the caves formed.