A sentence which punctuated correctly below is B. Bertie was proud of his new title: Vice President in charge of Special Tasks.
Punctuation are used in writing to clarify the meaning of the sentence or to separate elements in the sentence.
Some of the punctuations marks are period, comma, semicolon, apostrophe and so forth.
The above phrase is punctuated correctly because it applies the appropriate usage of a colon.
Colon is one of the punctuation which is used to:
1. Lay emphasis
Example: He loved just one: Bruno, his dog
2. To present dialogue ( we write the name of the speaker and then insert colon followed by his/her dialogue.)
Example: Rita: How are you?
Mary: Fine, and you?
3. Clarify composition titles ( to explain parallel ideas colon is used in compositions like lectures or book titles), and
Example: Rousseau’s Dog: Two Great Thinkers at War in the Age of Enlightenment
4. To introduce text or lists.
Example: Three types of Subordinate or Dependent Clauses are: Adjective clause, Adverb clause and Noun clause
Hence, in the above sentence, the sentences clarifies two parallel ideas "Bertie was proud of his new title" and "Vice President in charge of Special Tasks."