Answer: Explanation:
The sentence presents one situation where some facts ("mom had to work late;" "and the storm knoked out the electricity") are part of a cause, which <em>had an effect on another fact, or a consequence of the initial facts,</em> ("so we had to eat cold cereal for supper.") Mom couldn´t cook because she was at work; without electricity and no microwave <em>resulted in 'cold cereal for supper.' The conjunction so is used to say that something happens as a result of something else.</em>
The date of a business letter is included in the B Heading