The answer to this question is Surveys
Survey is the data collecting method that easy to be done because it collect informations from wide variety group of people, especialy after the development of internet. Not only that, these type of data usually could target questions that usually private and unable to be told in public.
This type of system is called representative democracy. This is when the majority of the people vote for a person for a specific position during an election process. This person will represent them by making decisions in the best of their interests.
Answer:
D. By adding the vectors

Explanation:
Given
Represent the velocity of the river current as VR

Represent the velocity of the boat as VB

Required
How to calculate the velocity of boat relative to river current
From the question, we understand that both move in the same direction.
So, the relative velocity V is calculated as:



Notice that the both velocities are added together to get the relative velocities.
This is so because they both move in the same direction
<em>From the list of given options, only option D is correct.</em>