B. C. pitch and volume
D frequency
11. Mike invented a backpack to help protect students' backs when they carry
their books home from school. He showed his idea to some other students
and got their opinions. The students suggested some changes. What should
he do next?
A. revise his design
B. ignore the opinions of other students
C. forget about his design
D. keep showing his design to other students until he finds students who
like it

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.