Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

[Q]: Photons have no mass and ____ electrical charge.
[A]: no


[Q]: Neutrons consist of one up quark and ____ down quarks.
[A]: two


[Q]: Pairs encodes all sets of objects with ____ components.
[A]:
two