苏云金杆菌产生的毒素是（）。
参考答案：蛋白质晶体毒素
A pension fund expects to pay obligations of $ 5000000 4 years from today. The fund will fund this obligation by making 5 annual, equal deposits into an account earning 3% , with the first deposit occurring today, and the last occurring at the time the obligation is due. What size must each annual deposit be（）
A. $ 904874.
B. $ 941773.
C. $1125662.
A．若穿过线圈平面的磁通量最大，则该处磁感应强度一定最大
B．若穿过线圈平面的磁通量为零，则该处的磁感应强度也为零
C．在磁场中某处，穿过线圈平面的磁通量只与该处的磁感应强度和线圈的面积有关
D．在磁场中某处，若穿过线圈平面的磁通量最大，线圈平面应与磁场方向垂直放置
