Blood Type Compatibility. Your ABO blood type is based on the presence or absence of the A and B antigens on your red blood cells. The A blood type has only the A antigen and the B blood type has only the B antigen. The AB blood type has both A and B antigens, and the O blood type has neither A nor B antigen.
Green Triangle. The green triangle appears in the upper left hand corner of a cell when there is an error in a formula. Sometimes Excel will report an error when you use text in a box and the program believes it is part of a formula. When you click on the green triangle there will be a yellow box that looks like a road sign with an exclamation point in it. This button is the Trace Error option that will help you correct your formula.
Click on the top left cell in your array, drag the cursor to the opposite corner (to highlight all cells in your array) and release the cursor. Then click on the down arrow beside the Name Box near the top left corner of the Excel window. &nbsp The reference to the top left cell in your array is highlighted.