换板报太麻烦，做完不要轻易换（   ）

已知 $\text{cos}\left(\frac{\pi }{4}-\frac{\theta }{2}\right)=\frac{2}{3}$ ，则 $\text{sin}\theta =$ （    ）

甲船从A港出发，每小时行18千米，5小时后，乙船出发9小时追上甲船，乙船的速度是____ ．

磷是植物生长的重要营养元素之一，为了从土壤中筛选出能够将难溶性磷酸盐转化为植物能吸收的可溶性磷的优良解磷菌株，以便将其添加到有机肥中，改善植物磷元素供应．科研人员进行如下实验：

实验原理：固体培养基中难溶性磷酸盐在微生物作用下溶解，会在菌落周围形成透明圈，透明圈直径（D）与菌落直径（d）的比值（D/d）代表微生物溶解磷的能力大小．

实验步骤：步骤1 取某地区土样5g制得土壤溶液后稀释，取稀释液1mL接种到基础培养基A上，在适宜温度下培养72h．步骤2在基础培养基A上用接种环挑取代表性菌落再次接种，培养3～4d后观察菌落特征和透明圈的大小，初步筛选出三种优良解磷菌株（如表）．

菌株	透明圈直径 （D）单位：mm	菌落直径 （d）单位：mm	D/d
甲	22.8	15.3	1.5
乙	20.7	7.7	2.7
丙	8.2	7.5	1.1

请分析回答下列问题：

根据短文内容，选择正确答案。
A
    One day, Mr. and Mrs. White went shopping by car. They stopped their car near a store. They bought a lot of things and they wanted to put them in their car. But Mr. White couldn't open the door of the car. “Let's ask a policeman for help.” said Mrs. White. They asked a policeman to help them. The policeman was very friendly to help them open the door of the car. Just then a man came up and shouted, “What are you doing with my car?” Mr. and Mrs. White took a look at the number of the car. It was not their car.