The correct answer is A.
Poor Richard’s, which was published once a year, was a collection of miscellaneous information.
Step-by-step explanation:
In writing, combining sentences means creating one sentence with the information of two or more sentences, this implies the new sentence should include the original meaning of both sentences and mixing both using correct grammatical structures. In the case sentence 6 and 7 these sentences can be combined by omitting the use of "PoorRichard's" twice and just putting together the details provided in both either with a subordinate clause such as "which" as in "Poor Richard’s, which was published once a year, was a collection of miscellaneous information" or coordinate conjunction such as "and" which will result in the sentence "Poor Richard's was published once a year, and was a collection of miscellaneous information".
Considering this, the most effective way to combine these sentences is "Poor Richard’s, which was published once a year, was a collection of miscellaneous information"(first option), because in this way unnecessary repetition is avoided, the details of both sentences are included and this is the only option that is grammatically correct as the rest of the options try to use the conjunction "and" and other grammatical forms but are not complete and therefore grammatically incorrect.