There are two high and two low tides in a day. give reasons

Their are two low tides and two high tides during the day because the gravitational pull of the moon is at the specific angel needed to create the fluctuation in tides twice a day 

It is the doctrine that the us had the right and duty to expand throughout north america. it just means they believed they had the right to expand westward and they did! they stated with the 13 colonies and then they kept moving gaining different territories throughout the years