Why is it difficult to identify the cause of many nervous system disorders?
the genes associated with the diseases are not known.
there are no obvious defects in brain structure.
the onset and display of symptoms varies between patients.
all of the above

1. b.

2. d.

3. a.

5. d.

6. c.

these are the only ones that i know, i hope this , and good luck.

ionic bonds are two oppositely charged ions that attract. a sodium ion has a 1 positive charge; a chloride ion has a 1 negative charge. sodium and chloride have oppostive charged ions that attract which forms an ionic bond. a chemical bond formed when two atoms share electrons is called