1. I took my dog to the park, but becauseit was crowded,its mood changed.
The sentence is incorrect because in a sentence, all the pronouns should refer to the same noun. The first IT refers to THE PARK. The second IT is incorrect because it refers to yet another noun. Had it refered to PARK again, it would have been correct.
2. I took my dog to the park, but becauseit was crowded,it started barking.
For the same reasons stated above.
3. Because white diamonds require more refined polishing,
...
The sentence is incorrect because in a sentence, all the pronouns should refer to the same noun. The first IT refers to THE PARK. The second IT is incorrect because it refers to yet another noun. Had it refered to PARK again, it would have been correct.
2. I took my dog to the park, but becauseit was crowded,it started barking.
For the same reasons stated above.
3. Because white diamonds require more refined polishing,
...
