The survey among 25-65 year olds focused on________.

The number of students participating in online courses varies 　. A: year to year B: year and year C: year by year D: year on year

In ancient China, people paired items from Heavenly Stems and Earthly Branches respectively to mark the year, and sixty years form a cycle.

This year is the year of Gengzi, and next year is the year of ___________.

判定year是否为闰年的表达式是 A: year % 400 == 0 or year % 4 == 0 and year % 100 <> 0 B: year % 400 == 0 or year % 4 == 0 , year % 100 != 0 C: year % 400 == 0 or year % 4 == 0 and year % 100 != 0 D: year % 400 == 0 or year % 4 == 0 , year % 100 <> 0

21（） A: next year B: that year C: this year D: by year

使用变量year代表年份，以下表示判断year是否为闰年的布尔表达式是 。 A: (year % 4 == 0) and (not(year % 100 == 0)) or (year % 400 == 0) B: (year % 4 == 0) and (not(year % 400 == 0)) or (year % 100 == 0) C: (year % 4 == 0) and (year % 100 == 0) or (year % 400 == 0) D: (year % 4 == 0) or (not(year % 100 == 0)) and (year % 400 == 0)

题:(拓展)下面哪些表达式能够判断某年year不是闰年。 A: not(( year%4==0 and year%100 !=0 ) or ( year%400==0 )) B: not( year%4==0 and year%100 !=0 ) and not ( year%400==0 ) C: year%4!=0 or year%100 ==0 and ( year%400 !=0 ) D: year%4==0 and year%100 !=0 or ( year%400==0 )

判断year变量为闰年的表达式为（）。 A: year%4==0&amp;&amp;year%100!=0&amp;&amp;year%400==0 B: year%4==0||year%100!=0&amp;&amp;year%400==0 C: year%4=0&amp;&amp;year%100<;>;0||year%400=0 D: year%4==0&amp;&amp;year%100!=0||year%400==0

In ancient China, people paired items from Heavenly Stems and Earthly Branches respectively to mark the year, and sixty years form a cycle. A: 正确 B: 错误