Answer: B. 

Step-by-step explanation:
Let
be the proportion of all U.S. adults that smoked in 1995. Let
denote the proportion of all U.S. adults that smoked in 2000.
Objective for the study : Whether the proportion of U.S. adults that smoke declined during the 5-year period between the samples.
i.e. 
Alternative hypothesis
is the statement containing population parameter that shows there is significant difference between the groups being tested.
⇒ 
Null hypothesis
is the statement containing population parameter that shows there is no significant difference between the groups being tested.
⇒ 
Hence, The hypotheses to test in this problem are


Hence, the correct answer is B. 
