求教语法问题

askfjaw

173.

The widely accepted big-bang theory holds that the universe began in an explosive instant 10 to 20 billion years ago and has been expanding ever since.

• A.that the universe began in an explosive instant 10 to 20 billion years ago and has been expanding
• B.that the universe had begun in an explosive instant 10 to 20 billion years ago and had been expanding
• C.that the beginning of the universe was an explosive instant 10 to 20 billion years ago that has expanded
• D.the beginning of the universe to have been an explosive instant 10 to 20 billion years ago that is expanding   
• E.the universe to have begun in an explosive instant 10 to 20 billion years ago and has been expanding
• 请问本题目答案为A，但是一般自然现象不是用一般现在时吗，为什么本题目用的是一般过去时
  

Fiona09

那是指不受时间限制的普遍真理和自然规律，这里明显有时间指示词——10 to 20 billion years ago，得用过去式