In what shape/shapes are the diagonals always perpendicular

A Rhombus, Square

Step-by-step explanation:

 produces an irrational number when added to 0.5

Step-by-step explanation:

Notice that the number 0.5 is a rational number (not irrational), because it can be written as the quotient of two integer numbers (1 divided by 2),\.

So in order to obtain an irrational number added to such rational number , the only possibility is to add to it an "irrational number." The addition of another rational number will again generate a rational number, and not an irrational one.

Out of the list of numbers shown, only is an irrational number, so it is the only one that added to 0.5 can render an irrational number.

Notice that there is another option listed with a square root () but such root can be simplified to a rational number : "4".