函数$f\left(x\right)=3\sin \frac{\pi }{2}x-{\log }_{\frac{1}{2}}x$的图象与x轴交点的个数是(   )

改革开放以来，我国设立了深圳等经济特区。经济特区的设立（  ）

Dear Mum,

    How are you?

    I'm very well in Shanghai. It's a beautiful city. I like the place. And I made a new friend. Her name is Huanhuan. She's got long and black hair. She's got big eyes. She is tall and thin. She's clever. But she is a bit shy. She likes English best. And she works hard. She often helps me. I miss you. I will be back next month.

Love,

Belinda

荠菜的果实形状有三角形和卵圆形两种，该性状的遗传由两对等位基因控制。将纯合的结三角形果实荠菜和纯合的结卵圆形果实荠菜杂交，F₁全部结三角形果实，F₂的表现型及比例是结三角形果实植株∶结卵圆形果实植株＝15：1。下列有关说法，正确的是(　　 )