Last year the rate of inflation was 1. 2 percent, but during the current year it has been 4 percent. We can conclude that inflation is on an upward trend and the rate will be still higher next year. Which of the following, if true, most seriously weakens the conclusion above? ['The 1. 2 percent rate of inflation last year represented a 10-year low.', 'The inflation figures were computed on the basis of a representative sample of economic data rather than all the available data.', 'Increases in the pay of some workers are tied to the level of inflation, and at an inflation rate of 4 percent or above, these pay raises constitute a force causing further inflation.', 'Last year a dip in oil prices brought inflation temporarily below its recent stable annual level of 4 percent.']