Step-by-step explanation:

What is the sample space if a coin is tossed twice?

Your tuition teacher is right the sample for a coin tossed twice is {HH,HT,TH,TT}

let me explain you mathematically

the sample space for a coin which has two outcomes(H or T) based on the following formula

2 raise to the power of no of coin you are tossing

for one coin tossed or a coin is tossed once

2^1=2 (H,T)

for one coin tossed two times or two coins tossed simultaneously

2^2=4(HH,HT,TH,TT)

for one coin tossed 3 times or 3 coin tossed simulatenously

2^3=8

In your case it is given that a coin is tossed twice so the out come for you case is

2^2=4

four out comes (HH,HT,TH,TT)