若田间一次施肥过多，就会使作物变得枯萎发黄，这一现象俗称“烧苗”。其原因是（  ）

自耕农经济是封建经济的基本形式。下面对这一经济形式的认识不正确的是（   ）

阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空。

    It was a very special day because Dylan Terry came to the West EndChildren's Home! Dylan Terry is my favorite ____ (sing). I like him because he sings ____ (wonderful), he’s cute and he helps the kids alot.

    We ____ (stand) near the door, waiting for him.Everyone was very excited. Finally, he    arrived ____ shook hands with us. He was so nice! He sang several songs for us. Some of us evenstarted dancing ____ he was singing. We were having a great time!

____ our surprise, Dylan joined us for lunch. Hebrought us ____ big cake. Everyone ate some and ____ was delicious. While we were eating, Dylantold us many interesting ____ (story) about himself. I never thought I couldtalk to my favorite pop star. It was just like a dream. I ____ (remember) this unforgettable experienceforever.

高铁酸钠（Na₂FeO₄）是水处理过程中使用的一种新型净水剂作剂，它的氧化性比高锰酸钾更强，本身在反应中被还原为Fe²⁺离子．配平制取铁酸钠的化学方程式：____Fe（NO₃）₃+____NaOH+____Cl₂═____Na₂FeO₄+____NaCl+6NaNO₃+8H₂O．反应中，____元素被氧化，每生成8mol H₂O转移电子总数为____．

如果集合$M=\left\{y\right|y=\frac{\sin x}{\left|\sin x\right|}+\frac{\left|\cos x\right|}{\cos x},x\ne \frac{k\mathrm{\pi }}{2},k\in Z\}$，则M的真子集个数为（   ）