Can you please explain which of the following XML documents are well-formed?
A. <firstElement>some text goes here
<secondElement>another text goes here</secondElement>
</firstElement>
B. <firstElement>some text goes here</firstElement>
<secondElement> another text goes here</secondElement>
C. <firstElement>some text goes here
<secondElement> another text goes here</firstElement>
</secondElement>
D. </firstElement>some text goes here
</secondElement>another text goes here
<firstElement>
