Which one is NOT an example of a tangible benefit?

I think it is option no 4. Better decision making

Project Benefits can be tangible which means the benefit can be measured or quantified. The tangible benefits are generally in dollars or time saved. The time saved can be converted to dollars by applying a hourly rate or daily rate.

Increased Revenue 

The most common type of benefit and a very broad category. 

Increased revenue is a benefit when a project has a direct impact on the revenue of the organisation. 

The additional revenue  could be coming from a new product launch or by providing an offer that could attract an existing customers.

When stating revenue as a benefit make sure you put a precise dollar value against the benefit. Also, add an additional information you have so that the person reading your case will get all the details they need.

Examples are increased sales or increased subscription.

Yes, Option4 is the right answer.

option4 -----------------------------------------------------------------------

correct answer is option4

Better decision making

Decision making because favorable decision become intangible asset of business in sense of Goodwill etc.

may be the better decision making.