What is the main way scientists measure the extent of snow and ice cover in the
Arctic and Antarctic?
A. data collected from boats
B. photographs taken from helicopters
C. images taken by satellites
D. estimates developed by computer
models

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

the correct answers are;

a. the rock was made from more than one type of material.

e. layers of hot liquids in the rock cooled and solidified at different temperatures.

these are the two options that are related to the statement given above.

1. the geologists have established a set of principals that can can be used o determine the relative ages of rock. this principal is applied to sedimentary and volcanic rocks. the rocks exposed to wall of grand canyon has layers and by studying the number of horizontal layers in the rock(strata) the relative age can be determined. the layer first formed will appear at the bottom and the the layer of strata last formed appear at the top. by using this information the approximate age of rocks can be determined.

2. carbon dating is used to find the relative age of rock in numbers which means for the rocks that has age between 1-70,000 years.

3. for the rocks of age range between 1,000 - billion of years potassium-argon dating is used.