设NA为阿伏加德罗常数的值，下列关于2L0.2mol•L-1的Ba（NO3）2溶液的说法不正确的是（ ）
①溶液中的阴、阳离子总数为0.8NA
②取0.5L溶液则其中NO3-的浓度为0.1mol•L-1
③取0.5L溶液则其中Ba2+的浓度为0.2mol•L-1
④取0.5L溶液则其中NO3-的总数为0.2NA．
A．①②
B．③④
C．①④
D．②④
①2L 0.2mol•L-1的Ba（NO3）2溶液中，含有0.4mol硝酸钡，含有0.4mol钡离子、0.8mol硝酸根离子，阴、阳离子的总物质的量为1.2mol，总数为1.2NA ，故①错误；
②溶液的浓度与溶液的体积无关，所以0.5L溶液中NO3-的浓度为0.2mol•L-1 ，故②错误；
③根据②的计算可知，取0.5L溶液则其中Ba2+的浓度为0.2mol•L-1，故③正确；
④0.5L溶液中含有0.1mol硝酸钡，含有0.2mol硝酸根离子，NO3-的总数为0.2NA，故④正确；
故选：B．
完形填空（共10小题；每小题1分，满分10分） Having a few days off always sounds so great. Everyone needs a 1 . And so does US President.US President Barack Obama went on holiday with his family in 2 in 2011. Where did they go and did the first family enjoy 3 ? Now, Obama is trying to 4 his experience (经历) with us. Let’s listen to him. “We travelled to Honolulu, Hawaii, in December 2011 for 5 . Of course we went there by air. We spent 17 days there. Hawaii is my hometown. We had a wonderful time there. This was one of the 6 vacations in my life. My wife Michelle and I visited US Marines (海军) and their families in Hawaii on Christmas Day. I 7 held the eight-month-old baby of a captain in my arms. I also spent part of Christmas Eve playing golf with my old friends from Hawaii and some White House staff. I went to Hanauma Bay Nature Park with my 8 daughters. That’s our favourite place. We dived there, 9 set four sea turtles free. We all had a good time. And both my daughters said that they wanted to go there for a 10 time later.”
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