Answer:
3. Tails of phospholipids are hydrophobic.
Explanation:
According to the fluid mosaic model, the plasma or cell membrane contains components such as: proteins, phospholipids etc. The phospholipid forms a layer called PHOSPHOLIPID LAYER, which comprises of a phosphate head and a fatty acid (lipid) tail.
The phosphate head is HYDROPHILIC i.e. water-logging while the fatty acid/lipid tail is HYDROPHOBIC i.e. water-fearing. Hence, according to this question, it is TRUE that the tails of phospholipids are hydrophobic.
Note: Phospholipid layer, which are selectively-permeable i.e do not allow the passage of molecules, allows the passage/diffusion of small molecules like oxygen gas.
Conduction - by touch
Convection - hot air rises, cold air sinks
Insulation - to insulate or capture heat
Radiation - by waves
Direct contact means touch, therefore the answer would be conduction.
