Select the word which means the same as the group of words underlined in the given sentence.
"These glass windows are so old and one can’t even see through them, they need to be replaced."

Let's evaluate the meanings of the options:
* Opaque: Not able to be seen through; not transparent. This matches the description perfectly.
* Transparent: Allowing light to pass through so that objects behind can be distinctly seen.
* Dirty: Covered or marked with an unclean substance.
* Black: Of the very darkest color owing to the absence of or complete absorption of light.