To determine which option weakens the given statement, let's analyze each option in relation to the goal of reducing the import surplus while resuming economic growth:

A. Economic growth will result in a structural change of the economy.
This option supports the statement by suggesting that economic growth will bring about the necessary structural change in the economy to reduce the import surplus. It does not weaken the statement.

B. Only if people consume less can the economy grow.
This option supports the statement by suggesting that reducing consumption is necessary for economic growth and reducing the import surplus. It does not weaken the statement.

C. The import surplus can be reduced if investment is restricted.
This option weakens the statement by suggesting that restricting investment can reduce the import surplus. It implies that reducing investment, rather than a structural change, is the key to achieving the goal. However, it does not address the resumption of economic growth, which is also an objective.

D. Only a structural change in the economy can substantially increase imports.
This option does not weaken the statement but rather supports it by suggesting that a structural change in the economy is necessary to increase imports. It does not address the goal of reducing the import surplus.

E. People will have to be persuaded to give up consumption for the national good.
This option weakens the statement by suggesting that people need to be persuaded to give up consumption. It implies that reducing consumption may be difficult and requires persuasion, which may hinder the goal of reducing the import surplus while resuming economic growth.

Based on the analysis, option E: People will have to be persuaded to give up consumption for the national good weakens the statement the most. It implies that reducing consumption may not be easily achievable and may require persuasion, potentially challenging the goal of reducing the import surplus while resuming economic growth.