请教大家几个英语语法问题，请多多指教，谢谢！

①I take it (that) you are just visiting someone.
句中take it意思是认为、猜想，后面加that从句，that可以省略。

②Can not you figure that out based on my date of birth？
句子中的based是过去分词而不是动词的过去式，过去分词可以充当状语修饰句子。
例如，Located at the foot of the mountain, the village attracts many tourists every year.
The book based on ramance story has a great many readers.

③正确的句子为
You are two centimetres dilated.
You are dilated by two centimetres.
第一句的句子结构相当于 I am 12 years old. 结构为数字+名词（单位或者时间）+形容词。
而像第二句一样，dilated如果放到前面，必须加数字前加介词by表示程度。例如：He is older than me by 2 years. （他比我大两岁）

④I do not think the next patient is very far along.
far和along在此处都是副词。意思是“我认为下一个病人的（病情）没有很严重”。
再比如，How far along have you gotton? 你进展得怎么样了？
far along表示程度，需要根据具体语境来翻译。