Option C and D
My dog is beautiful; her eyes are her best features is correct because the semi colon show details of the connection between the independent clauses and it shows that “the dog is beautiful” is supported by the other clause, “her eyes are the best feature”.

Option D is also correct because a period can be used to show the connection between the two clauses. Option A is not correct because it is not punctuated and the clauses have to be linked by punctuation.

Option B is also wrong because a comma does not show a strong connection between the independent clauses. It can only be used in a continuing sentence not to link independent clauses

My dog is beautiful; her eyes are her best feature.-2. my dog is beautiful. her eyes are her best feature.-a is incorrect because there are two independent clauses, so some punctuation is definitely needed. b is not right because a comma isnt strong enough to connect two independent clauses. in c, the semicolon is used. this is a good answer because the idea expressed by my dog is beautiful is directly supported by her eyes are her best feature. the two statements are inextricably linked, so the semicolon can be used. d is also correct because two independent clauses can always be linked by a period. for more info on these rules, see the st. martins handbook, chapters 39, 49, and 50.