Answer: 

Step-by-step explanation:
- A null hypothesis is a hypothesis where a researcher generally try to disprove, it says that there is no statistically significant relationship between the two variables .
- An alternative hypothesis says that there is a statistical significance between two variables.
Claim 1. : Mean age of online dating service users is 40 years.
i.e.
, since it has equals sign so we take this as null hypothesis.
Claim 2. : Mean age of online dating service users is not 40 years.
⇒ Null Hypothesis : 
Alternative hypothesis : 
Answer: Choice D 
Reason:
Exponential functions have the variable in the exponent.
Choice A is a polynomial, which means we can rule it out. Choice B is a log function, so we can rule it out also.
Choice C is a rational function because it is a ratio of two polynomials. This rules out choice C.
Choice D is the only function with the variable in the exponent. That is assuming you meant to say
instead of 
The speed of the current is 7 miles per
hour.
Step-by-step explanation:
Let × represent speed of the current.
We have been given that a motorboat
maintained a constant speed of 11 miles per
hour relative to the water in going 18 miles
upstream and then returning.
The speed of motorboat while going
upstream would be 11
The speed of motorboat while going
downstream would be 11 + 2
Time
Distance
Speed