During which period was England governed as a republic, without a monarch?

Okay, let's talk about that brief period in British history when there was no king or queen. This happened in the mid-17th century. King Charles I had a lot of disagreements with Parliament about how the country should be run, which eventually led to the English Civil War. Charles believed in the Divine Right of Kings, meaning he thought God had given him the authority to rule, but Parliament wanted more say in things. After a long and bloody conflict, Charles I was captured, put on trial, and executed in 1649. This was a really shocking event at the time! With the king gone, England became a republic known as the Commonwealth, led by Oliver Cromwell. So, the execution of Charles I is the key event that directly led to England being governed without a monarch. The other options refer to important moments in British history, like the Magna Carta which limited royal power, but they didn't result in the abolition of the monarchy itself.
The execution of Charles I marked the end of the monarchy and the beginning of the Commonwealth.