It was snowing hard_______we had to stay at home and watch TV.
A:that
B:so
C:but
D:because
(Ⅰ)求数列{an}的通项公式;
(Ⅱ)设数列{ 1anan+1 }的前n项和为Sn,求证: 14 ≤Sn< 13 .
在酿酒的过程中,酵母菌发酵不需要的生活条件是( )
欲将含有盐酸的氯化钙溶液中和至中性,在不用指示剂的条件下,应加入的试剂是( )