Language Points
1.Krista, his friend, noticed him looking sad.他的朋友，Krista，注意到他看上去很伤心。
notice sb. doldoing sth.注意到某人做/正在做某事例子:l noticed her looking at me when I turned
around.
我转过身的时候注意到她正看着我。

2. He worked very hard, both by himself and withKrista.无论独自一人时还是和克里斯塔时，他学习都非常努力。
(1)by oneself意为“单独地，靠自己地(alone orindependently)”。如:
例子:All his friends have deserted him and heis all by himself now.他所有的朋友都离弃他了，现在他孤独一人。

(2)both用作形容词，意思是“二者的，双方的”作。还可作代词，意思是“二者都”位于行为动词前，be动词后。
例子:His parents are both teachers and they both work hard.
他的父母都是老师，他们工作都很努力。