If triangle rst is an acute triangle, then m∠s must be? less than 90°. equal to 90°. equal to 100°. greater than 90° and less than 180°.

m∠S must be less than 90° ⇒ first answer

Step-by-step explanation:

* Lets talk about the types of the triangles according to the measures

 of their angle

- The acute angle triangle:

# Its three angles are acute angles

- The right angle triangle

# One of its angle is right angle and the two other angles are acute

- The obtuse angle triangle

# One of its angle is obtuse angle and the other two angles are acute

- From all above any triangle has at least two acute angles

* Lets revise the measure of the angles

- The measure of any acute angle is greater than 0° and less than 90°

- The measure of the right angle is 90°

- The measure of any obtuse angle is greater than 90° and less

  than 180°

* Lets solve the problem

∵ Triangle RST is an acute triangle

∴ Its three angles are acute angles

∵ The measure of the acute angle is less than 90°

∴ The measures of the three angles is less than 90°

∴ m∠S must be less than 90°

sorry, i can't understand your question. will later if you describe more clearly!

: )