Ok here we have two examples of linear functions. A linear function consist of a variable (in this case x which represents years) and two parameters: the slope (in this case 2.5 which represents how much D(x) increses when x increases) and the intercept (149.5 which represents the inical value of D(x) when x=0). D represents the number of houses with access to a telephone.
Let's check which of the items is correct:
In item A the speak about the number of houses with access to telephone (D) in 1965. Since x represents the years past after 1965 then if the year is 1965 then x=0.
And D=2.5*0+149.5=149.5. So there were 149.5 thousand homes with access to telephone in 1965 and this item is correct. So the answer is A.