If someone tells me that scientific knowledge cannot be changed or modified how would i answer that statement

Scientific knowledge is constantly being refined and changed as scientists perform studies using the scientific method.  New discoveries such as the recent discovoery of water on Mars, cause scientists to re-evaluate their previously held theories.  

Read the sentences below in 1962, i tried to enroll as the first black student at the university of mississippi. the governor of mississippi blocked my entrance which best describes the verbs used in the sentences? o they are past tense verbs, which are often used in narrative essays o they are past tense verbs, which are not often used in narrative essays. o they are future tense verbs, which are often used in narrative essays o they are future tense verbs, which are not often used in narrative essays.