`stackrel(harr)(AB)` is perpendicular to `stackrel(harr)(CD)`. How many 90° angles are formed by the intersection?

Click the item in the left column. use the plus sign to move it up or the minus sign to move it down until it matches the correct entry in the right column. lock your answer in place by clicking the square beside the item. (a checkmark means it is locked.) amazon basin a atacama desert b andes mountains c lake titicaca d peru e patagonia f brazil g chile h suriname

Why the moon is not visible from earth during the new moon ?

How many years is a term in the senate