如图所示，太阳光线与水平面成30°角，要利用太阳光垂直照亮井底，应把平面镜放在跟水平面成____度角的位置，在图中画出平面镜的位置____。

设函数 $y=f\left(x\right)$ 的定义域为 $D$ ，值域为 $A$ ，如果存在函数 $x=g\left(t\right)$ ，使得函数 $y=fg\left(t\right)$ 的值域仍是 $A$ ，那么称 $x=g\left(t\right)$ 是函数 $y=f\left(x\right)$ 的一个等值域变换.

读《简·爱》，罗彻斯特虽富有而显赫，却是一个____。同时，外表奇特甚至可以说是丑陋的他有是一个____的强大者

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    Friendship is a kind of human relationship. It is a human instinct to make friends. When ____ trouble, we need friends to offer us help, support and encouragement. With success achieved, we also need friends to share our joys.
    Friendship is also one of the greatest ____ (pleasure) that we can enjoy. It implies loyalty, cordiality, sympathy, affection and readiness to help. No man can make ____ most of his life  without ____ (careful) and conscientiously（认真地）struggling to win the right kind of friends as he ____ (go) along.
    Knowing how ____ (value) friendship is, we should be very careful in making friends. Real friends are those who have good character, superior ability and kindness of heart. Real friends can share all our sorrows and double all our joys. ____making friends, we should take care ____ (select) those who have such fine qualities. We should forgive their failures and do our best to help them. In short, when we have established friendship, we ought to cherish and treasure it ____ means of words and deeds. Only thus, can we develop real friendship and keep the sacred lamp of friendship ____ (burn) all of life.

民营手工业不同于官营手工业的表现有（   ）

①规模小

②产品与老百姓生活关系密切

③价格比较准确地反映市场规律

④与商业联系比较松散