Which letter from the Greekalphabet is the symbol of the most penetrating type of radiation containing no particles ?
which letter from the greekalphabet is the symbol of the most penetrating type of radiation containing no particles 
FreebaseQA-train-8523.P0
greekalphabet
greek alphabet
m.0358gm
user.tsturge.language.alphabet.letter
m.036yp
gamma