Pick correct statements from among the following : 

1. Electric field and magnetic field are basically independent 
2. Electric field and magnetic field are the two aspects of the electromagnetic field   
3. Electric field and magnetic field may be produced by charge at rest 
4. A moving charge produces both electric and magnetic fields.

a, b and d are correct

1. Electric field and magnetic field are independent.
2. They are two aspects of the electromagnetic field.
3. Charge at rest only produces electric field.
4. Moving charge produces both electric field and magnetic field.