Both sentences A and B are capitalized correctly:
Only one solution is possible: We must cut our expenses.
Only one solution is possible: we must cut our expenses.
The first word of both sentences (only) must always be capitalized since it is placed at the beginning.
On the other hand, if the sentence following the colon is dependent (it is incomplete), its first word should not be capitalized. For example:
"I have to buy three things: apples, oranges and bananas."
Regarding capitalization in independent clauses following a colon (such as the one given in the example), it is subject to the citation style the writer is following (APA, MLA, etc). While some styles recommend capitalization of the first word of the sentence, some others do not.
<span><span>The best sentence that would summarize the general idea of the article is: For many centuries, people who spoke a variety of different languages tried to figure out the meaning of hieroglyphs. <span>
</span></span><span>This general thought summarizes the whole idea of the passage and gives a clear conclusion on what is being achieved in the story. </span></span>
Montresor offers him wine because he needs to get him drunk first before he's able to easily kill him.
“I am sick to death of cleverness. Everybody is clever nowadays.” “I've now realized for the first time in my life the vital Importance of Being Earnest.” - jack worthing
