A triangle cannot have

Sum of the three angles of a triangle is $180°$

$a\to$  If two angles are right angles then third angle will be $0°$ ,

so, we cannot form a triangle

$b\to$  Sum no any two obtuse angle is greater then$180°$ ,

So, we cannot form a triangle

$c\to$  Two acute angle

Sum of two acute angles is either acute or obtuse, (never exceeds$180°$ )

$d\to$  If all the angles are less than $180°$

So, a triangle cannot have all the angles less then $60°$