Answer:
Slippery, high pH, and caustic
(last option listed)
Step-by-step explanation:
sour taste - acid feature
pH < 7 - acid feature [low pH]
dissolves metal - strong acid feature
bitter taste - base feature
slippery feel - base feature
pH > 7 - base feature [high pH]
dissolves metal - strong base feature
[essentially, traits of base can be described as opposites of acid traits]
So, if you combine these traits, "Slippery, high pH, and caustic" best describes characteristics of a base