如果学生能够通过系统的假设检验得出钟摆的速度仅与绳子的长度有关，与重量、释放的高度及所受推力无关这一普遍法则，那么其认知发展处在（ ）。

(单选题)There ______ some juice, two eggs and a few cakes on the tab (单选题)Give me your email address, ______ I will send you the photo (单选题)I feel it hard to keep up with my classmates in Physics and (单选题)—I wonder ______ you’ll water the flowers.—Once a week. (单选题)Health is money, but it is ______ money. (单选题)The boy made his girlfriend ______ finally after he told her (单选题)—Can I help you?—I’d like ______ for my son. (单选题)It was very hard for me to make a ______, but I decided to g (单选题)I don’t have to introduce her to you ______ you know the gir (单选题)It is nice of you to ______ so much time helping me to learn