All students need to have good study habits(习惯). When you have good study habits, you can learn things quickly. You also remember them easily. Do you like to study in the living-room? This is not a good place because it is usuallytoo noisy. You need to study in a quiet place, like your bedroom. A quiet place will help you only think about one thing, and you will learn better. Before you begin to study, do not forget to clean your desk. A good desk light is important, too. You are feeling tired easily if there is not enough(足够的) light.

同学们能够从一个细胞发育成为“小帅哥”或“小靓妹”，要经过一系列复杂的变化． 受精卵分裂发育成胚胎，胚胎发育的主要场所是（　　）