Discussion
A comparison between HPGe and NaI(Tl) detectors for recording spectrum of gamma-rays, it is observed that in general :
Answer: C
In general, HPGe has high energy resolution but low efficiency compared with NaI(Tl).
In germanium only about 3 eV is needed to create an electron-hole pair, against roughly 100 eV per photoelectron in a NaI(Tl) scintillator and photomultiplier, so far more charge carriers are produced and statistical fluctuations are much smaller. A typical HPGe detector resolves about 2 keV at 1332 keV, against about 7% (some 90 keV) for NaI(Tl).
NaI(Tl) contains iodine (Z = 53, against germanium's 32), which absorbs gamma rays strongly by the photoelectric effect, and it is grown in much larger crystals, so a typical NaI(Tl) detector stops more of the incident gamma rays. Hence both 'higher' and 'the same' are wrong, and option D reverses the comparison.
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