Can a rectangle also be a rhombus? explain.

No. A rectangle MUST have 2 pairs of parallel sides and all equal angles. 
A rhombus has 2 pairs or parallel sides with 2 pairs of equal angles.

No

Explanation:
There are some significant differences between the rectangle and the rhombus including:
A rectangle:
1- each two opposite sides are equal
2- all angles are right angles

A rhombus:
1- all sides are equal
2- each two opposite angles are equal but not right

Based on the above differences, we can conclude that a shape can never be a rectangle and a rhombus at the same time

Hope this helps :)