After estimating a trend model for annual time-series data,you obtain the following residual plot against time. 
The problem with your model is that
Definitions:
Inductive Approach
A reasoning method that starts from specific observations to develop general conclusions or theories.
Persuasive Claim
A statement or argument made with the intention of convincing others to adopt a certain belief, change an opinion, or undertake an action.
Adjustment
A minor change or modification made to improve a system, process, or document.
Warranty Period
The specific time period during which a manufacturer or vendor is obligated to replace or repair defective parts of a product.
Q13: Referring to Instruction 17-3,if the probability of
Q14: Referring to Instruction 12.17,which of the following
Q22: In selecting an appropriate forecasting model,which of
Q68: You need to proceed with extreme caution
Q98: Referring to Instruction 17-3,if the probability of
Q132: Referring to Instruction 13.36,the Head of Department
Q149: Referring to Instruction 12.17,what is the standard
Q160: Referring to Instruction 12.38,suppose the director of
Q161: The coefficient of determination represents the ratio
Q240: Referring to Instruction 13.20,to test the