The weakness of hydrogen bonds between the bases of dna allows what

The  weakness of hydrogen bonds between the bases of DNA allows for the easy separation of the two DNA strands during replication of DNA.

In replication, an initiator protein unwinds a short length of the DNA double helix. Next, an enzyme known as helicase attaches itself to the unwound helix and begins to break the hydrogen bonds between the base pairs  of the two DNA strands thereby pulling them apart to form a Y shape called a replication fork.

The  relative weakness of hydrogen bonds between the base pairs make it  fairly simple for helicase enzyme to beak them apart and thus the process is done very rapidly. 

the supermassive black hole is in the middle of the galaxy.

endo:

regulates body hormones, aldosterone, vasopressin

neural:

signal, regulates body using electric signals, reflex

endo has to do with hormones; aldosterone and vasopressin are both hormones. i also had this question and got it right : d