The plasma membrane in eukaryotic cells is primarily composed of phospholipids. Phospholipids are a type of lipid molecule that has a hydrophilic (water-loving) head and two hydrophobic (water-fearing) tails. These phospholipids are arranged in a bilayer structure, with the hydrophilic heads facing outward towards the surrounding environment and the hydrophobic tails pointing inward, creating a barrier that separates the inside of the cell from the outside.

Lipoproteins, on the other hand, are a combination of lipids and proteins. They play a role in transporting lipids in the blood, but they are not the main constituent of the plasma membrane.

Phospholipo-proteins and phospho-proteins are not accurate descriptions of the composition of the plasma membrane. There may be proteins associated with the membrane, but they are not the primary component.

In summary, the correct answer is option 1, phospholipids, as they make up the main structure of the plasma membrane in eukaryotic cells.