In an aqueous solution of ca(no3)2, which kind of attraction exists between the solute and the solvent?
1) london dispersion force
2) molecule-ion attraction
3) molecule-molecule attraction
4) hydrogen bond

In aqueous solution, Ca(NO₃)₂ dissociates in to Ca²⁺ and NO₃⁻ which both can be attracted to the water molecule since water molecules are very polar.  This means that molecule-ion attractions are present.   
If you can only put 1 answer put 3, but if you can have multiple answers technically London dispersion forces are present as well.  London dispersion forces are in practically everything it is just due to the fact that they are not very strong and are always present means that they are often times ignored.
I hope this helps.  Let me know if anything is unclear.

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.