Which particle cannot be accelerated by the electric or magnetic fields in a particle accelerator?

The neutrino is the particle that cannot be accelerated in a magnetic field.

To add, a neutrino is a subatomic particle that is very similar to an electron, but has no electrical charge and a very small mass, which might even be zero. 

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.