Statement-I: Giant stars live much longer than dwarf stars. Statement-II: Compared to dwarf stars, giant stars have a greater rate of nuclear reactions. Which one of the following is correct in respect of the above statements?

Answer: (d) Statement-I is incorrect, but Statement-II is correct

Giant stars burn their fuel much faster, so they live only millions of years; dwarf stars like the Sun live billions.

The idea

A star’s lifetime depends on its fuel supply divided by the rate at which it uses that fuel. Greater mass raises core temperature and makes fusion much faster. The extra fuel does not compensate for this much higher use, so massive stars have shorter lives. Strictly, “giant” describes an expanded stage of a star’s life, while mass is the main lifetime control.

Greater stellar mass → Stronger compression in the core → Higher core temperature → Faster nuclear fusion → Fuel used much faster → Shorter total lifetime

Why the others are wrong

(a) Statement I is wrong — giant stars live much SHORTER lives.

(c) Accepts I and rejects II — exactly backwards. Faster fusion (II) is WHY giants die young, so I is false.

The trap

“Giant” sounds like “long-lived”. In stars, size means speed of burning — and a shorter life.

Elimination technique

Faster reactions mean faster fuel use, not a longer life. In the question’s intended massive-star comparison, rejecting Statement I removes (a), (b) and (c).

Also know

A red giant need not have begun as a very massive star: the Sun will also become one. Low-mass stars can end as white dwarfs; sufficiently massive stars can undergo a core-collapse supernova and leave a neutron star or black hole. A red dwarf is a small hydrogen-burning star, whereas a white dwarf is a stellar remnant.