题目

Vitamin（维生素）D is called “sunshine vitamin，”and it is very important to health，yet more Americans are not getting enough，U．S．researchers said on Monday．Researchers found that 75 percent of Americans can’t reach the levels of vitamin D，up from about 50 percent of them 20 years ago．Getting enough vitamin D can be easy：spend 10 minutes in the sun with legs and arms exposed （暴露），or take vitamin pills．     “But people’s habits have changed…they are less active and outdoors less，and also protecting their skin from the sun because of skin cancer甲、乙两站相距448km，一列慢车从甲站出发，速度为60km/h；一列快车从乙站出发，速度为100km/h． (1)两车同时出发，相向而行，出发后多少时间两车相遇？ (2)两车相向而行，慢车先出发32min，快车开出后多少时间两车相遇？