A.
Select first the object that should be a child, press the CTRL key on the object that should be the parent, then press the SHIFT and P keys
B.
Select first the object that should be a parent, press the CTRL and left mouse button on the object that should be the parent, then press the CTRL and P keys
C.
Select first the object that should be a child, press the SHIFT and right mouse button on the object that should be the parent, then press the CTRL and P keys
D.
Select first the object that should be a parent, press the SHIFT and left mouse button on the object that should be the parent, then press the CTRL and P keys