It is multiple substance because it has different substances in it.
It depends on what 'easer' as in the question, means?
Life was easer in past than now.
A single substance has one phase.
Easer - helpmate
A single gene can influence multiple traits A single trait can be controlled by multiple genes
You can associate multiple credentials with a single scan
Multiple.
Single.
Blow my load.
Laser light has a single wavelength and is coherent, allowing for a well-defined interference pattern to be created easily. In contrast, Na-light contains multiple wavelengths and is not as coherent, making it more difficult to generate clear interference fringes.
The multiple reflection of a single sound wave is an echo.
A pure substance is a single element or compound, while a mixture is more than one atom or molecule. If there are multiple atoms, it would be a mixture.