[单项选择]施工企业的主营业务收入指( )。
A. 提供劳务收入
B. 让渡资产使用权收入
C. 承包合同收入
D. 销售商品收入

{{B}}Electronic Waste{{/B}}
It has been known since ancient times that certain plants regularly open
their leaves in daytime and close them at night. It was assumed which this 62. ______
periodic change was triggered by the alternating sunlight and darkness. Such
leaves stick to their daily routine even when keeping in constant darkness. 63. ______
What is circadian rhythm Many biological processes follow a 24-hours 64. ______
schedule. These cycles are called circadian rhythms. These innate rhythms are
governed by sophisticated chemical mechanisms can be described as biological 65. ______
clocks. Such rhythms are important for humans too! We sleep through most
of the hours of darkness and are awaken through most of the hours of 66. ______
daylight. Body temperature increases during the day and decreases during the
night. The secretio