Words or phrase (A, B, C or D) that must be changed for the sentence to be correct

Words or phrase (A, B, C or D) that must be changed for the sentence to be correct. 1. I (A) discovered something (B) interestingly (C) in the store so I (D) got in to buy it. 2. (A) Would you mind (B) help me solve these mathematics (C) problems? I can hardly understand (D) how to do them. 

3. She was (A) having dinner (B) when a man (C) was coming and giving her a (D) present. 4. Some people (A) grow so (B) taller (C) that their health (D) may become endangered. 5. After (A) said goodbye (B) to my parents, I (C) went to school (D) with my sister. 6. The (A) phone (B) rung while I (C) was washing the (D) dishes.