Final answer:
HF is a stronger acid than HCl, and neither PH3 nor NH3 are stronger acids than HF since PH3 is weaker than NH3, and NH3 is a base rather than an acid.
Step-by-step explanation:
The correct comparison is that HF is a stronger acid than HCl. Acid strength in binary hydrogen compounds typically increases with increasing electronegativity of the nonmetal atom and across a period in the periodic table, acid strength of binary hydrogen compounds increases.
Hence, HF, having fluorine which is more electronegative than chlorine in HCl, is the stronger acid. Similarly, NH3 is less acidic than HF since NH3 (ammonia) acts as a base, and HF is a well-known acid. Furthermore, PH3 is a weaker acid than NH3 since acidity generally increases down a group in the periodic table, and nitrogen is above phosphorus. Therefore, the comparison indicating that PH3 is a stronger acid than NH3 is incorrect.