<u>Part 1) </u>
we know that
The Centroid of a Triangle is the centre of the triangle that can be calculated as the point of intersection of all the three medians of a triangle.
The Centroid divides each median into two segments whose lengths are in the ratio 
so


we have

substitute

Find RZ


therefore
<u>the answer Part 1) is the option C</u>

<u>Part 2) </u>
Statements
<u>case A)</u> ∠BEC is an exterior angle
The statement is False
Because, ∠BEC is a internal angle
<u>case B</u>) ∠DEC is an exterior angle.
we know that
An <u>exterior angle</u> is formed by one side of a triangle and the extension of another side
therefore
The statement is True
<u>case C)</u> ∠ABE and ∠EBC are supplementary angles.
we know that
∠ABE+∠EBC=
-------> by supplementary angles
therefore
The statement is True
<u>case D) </u>∠BCF and ∠BEC are supplementary angles
The statement is False
Because
the only way that is true is that the triangle BEC is isosceles and that the ∠BEC is equal to the ∠BCE
<u>case E)</u> ∠BEC is a remote interior angle to exterior F.∠BCF
we know that
<u>Remote interior angles</u> are the interior angles of a triangle that are not adjacent to a given angle. Each interior angle of a triangle has two remote exterior angles.
In this problem ∠BEC has two remote exterior angles (∠BCF and ∠EBA)
therefore
The statement is True