Which type of change must occur to form a compound?
(1) chemical (3) nuclear(2) physical (4) phase

To form a compound, we need to change the structure of the molecules and mostly form new bonds between molecules to result in a compound.

A nuclear change changes the element completely and forms new elements, so nuclear is a wrong choice.
A phase change only changes the phase of the element (solid, liquid or gas) but does not change structure, so phase is a wrong choice
A physical change does not change the structure of the molecules, so physical is also a wrong choice.

On the other hand, a chemical change changes the structure of molecules and/or breaks/forms bonds.
Therefore, the right choice is chemical.

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.