An observer that moves with an electrical charge senses: a- a magnetic field b- an electric field c- electric and magnetic fields d- no field

Here observer is moving along with an electrical charge

now magnetic field on a moving charge is given by equation

electrical force on a moving charge is given by formula

so here we can say when observer is moving with the charge it will have two forces on it

1. magnetic force due to existing magnetic field

2. electric force due to electric field

so here he must have to experience both type of field presence

So here correct answer must be

C- electric and magnetic fields