"Liberty, therefore, is never real unless the Government can be called to account when it invades rights." Which one of the following is the best justification of the above statement?

The statement emphasizes that real liberty exists only when the government can be held accountable for violating rights.

A) In the realisation that the government can be brought to book in a court of law. This option directly provides the mechanism for holding the government accountable ("brought to book") when it invades rights, which is through the legal system ("court of law"). This is the most direct and practical justification for the statement.

B) In identifying a man as a political unit in a way which distinguishes him from other citizens. This discusses individual political identity, which is unrelated to the government's accountability for invading rights.

C) In a decentralized society wherein the basic needs of men can find satisfaction. While decentralization might offer some checks, it doesn't specifically address the mechanism of calling the government to account for invading rights. Satisfying basic needs is a separate concept.

D) In the understanding that liberty and, restraints are complementary. This is a general philosophical idea about the nature of liberty and its limits. It doesn't explain how the government is held accountable when it oversteps its bounds and invades rights, which is the core of the statement.

Therefore, option A is the best justification as it directly explains the practical means of holding the government accountable, which is essential for real liberty according to the statement.