Which signal are you talking about?
I am thinking the rock that forms from lava that cools quickly is D) Obsidian.
Answer:
a. lack of running water
Explanation:
The Tippy tap technology was invented to solve the issue of running water problem. This technology is designed mainly for hand washing and it is used in the rural area to solve the running water problem.
This technology technique needs only forty milliliters of water; it is less expensive and reduces the chance of transmitting diseases as the user only touches a bar of soap suspended by a string.
A is true
hope i helped :D
