D) Thermometer
A cool test to count syllables is to put your hand an inch or soon below your chin. Say the word slowly and count how many times your chin drops onto your hand.
Spaghetti has three syllables - your chin would touch your hand three times
Elephant also has three syllables
Mountain has two syllables - your chin would touch your hand two times
Thermometer has four syllables - your chin would touch your hand four times
Household has two syllables