To solve this problem, we need to understand the concept of the compressibility factor $Z$ for real gases.$\\$The compressibility factor $Z$ is defined as:$\\ Z = \frac{PV}{nRT} \\$For an ideal gas, $Z = 1.$ However, for real gases, $Z$ can be different from 1.$\\$If $Z < 1,$ the gas is more compressible than an ideal gas, indicating dominant attractive forces.$\\$If $Z > 1,$ the gas is less compressible than an ideal gas, indicating dominant repulsive forces.$\\$Given:$\\$• The gas has a molar volume 20\% smaller than that of an ideal gas under the same conditions.$\\$Let's denote:$\\ V_{ideal} =$molar volume of the ideal gas$\\ V_{real} =$molar volume of the real gas$\\$According to the problem:$\\ V_{real} = V_{ideal} - 0.2 \cdot V_{ideal} \\ V_{real} = 0.8 \cdot V_{ideal} \\$The compressibility factor for the real gas is:$\\ Z = \frac{V_{real}}{V_{ideal}} = \frac{0.8 \cdot V_{ideal}}{V_{ideal}} = 0.8 \\$Since $Z < 1,$ this indicates that the gas is more compressible than an ideal gas,$\\$suggesting that attractive forces are dominant.$\\$Therefore, the correct option is:$\\$Option 3: $Z < 1$ and attractive forces are dominant.