Why are watermelons so big? It is simply the nature of that particular fruit. You might just as well ask: "Why are kumquats so small?". That's the nature of kumquats.
yes, grapefruits are considered acidic because they are part of the citrus group which contains citric acid so yes
because grapefruits are actually hibrids from an orange tree so the orange could also get polinated from a grapefruit tree
Grapefruits usually have twelve segments.
yes grapefruits come from trees.
no they don't at all what so ever
All grapefruits (red or white) have seeds unless they are sold as seedless grapefruits. Even seedless grapefruits will usually still have some small pits in them.
no, are you high?
No.
3-3.3
Grapefruits and lemons are both citrus fruits.
No
No, they have a bitter tang. But not salty.