设a是实数，且$\frac{1+ai}{1+i}\in R$，则实数a=（　　）

【健康生活 快乐你我】中学生应该追求健康的生活，结合下列材料进行分析：

材料一：七年级（1）班举行了一次主题班会，班会主题是：判断日常生活中哪些是高雅的生活情趣，哪些是庸俗的生活情趣。许多同学提到了以下行为：①放学后去网吧上网；②节假日去旅游；③与朋友一起抽烟；④周末学画画，练书法；⑤上课看小说；⑥给同学起绰号。

    It's summer holidays. For Jacob, it means having a lot of free time to play with  ____ (he) friends. Usually, he isn't so excited about it, ____ (连词) this summer is different. This summer, he is going to see Justin Timberlake — one of his favourite singers

    Jacob got four tickets to Justin Timberlake's concert after he ____（win) an online singing completion （比赛） ____. (see) Justin Timberlake is one of his dreams (梦想), so it will something he will never forget.

    The biggest problem he had was  trying ____(choose) just three friends to go with him. He ____ (wish) that all his friends could go. He asked his mother ____(介词) help. She told him to choose people who also liked Justin Timberlake. Jacob thought it was ____ (冠词) good idea, so he chose three friends who liked Justin Timberlake as much as he did. He felt sorry for not____(take) his best friend Andrew, but he knew that Andrew didn't like Justin Timberlake' s music that much. Jacob's three friends were all very excited when he ____ (tell) them the good news.

    Now the concert is just a week away and Jacob can't wait any longer.

有关法国农业的正确叙述是（   ）