Fact 1: Amphibians have sense organs to smell and taste chemicals. Fact 2: Smell and taste belong to our chemical sensing system. Given the two facts above, amphibians have what sort of sensing system?

Select from the following.
[1]. strong
[2]. retina
[3]. four limbs
[4]. chemical
[5]. mechanical
[6]. the eyes
[7]. nerves
[8]. heat or cold
The answer is:
[4].