代码中的NameError，未定义'mars'

Question

第1行我收到错误，不知道问题是什么

Traceback (most recent call last):
  File "python", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'mars' is not defined

以下是代码：

x = int(input("what is the fourth planet in the solar system: "))
if x == mars:
    print ("correct")
else print ("incorrect")

Answer 1

您忘记了火星周围的引号，就像这个ADD

一样