Answer to Question 1
In the block letter format, all lines begin at the left margin. This format is efficient because the format is easy to remember, and paragraphs and other letter parts are not indented, which saves keying time.
The modified block style is useful for making a formal, traditional impression. The dateline, complimentary close, and signature block begin at the horizontal center. Paragraphs may or may not be indented.
Answer to Question 2
Letters using mixed punctuation style have a colon after the salutation and a comma after the complimentary close. Letters using open punctuation style omit the colon after the salutation and the comma after the complimentary close.
The 20 common amino acids used to build proteins
Every state has a two-letter abbreviation.
Common phlebotomy issues.
Some common eye disorders. (A) Conjunctivitis (“pinkeye”).
Structures of four common types of DNA-binding motifs from eukaryotic transcription factors
Staphylococcus epidermidis, a common colonizer of human skin.