Which organisms have many cells that are grouped together into tissues?

The correct answer is-  Multicellular organisms.

Multicellular organisms are those, which are made up of many cells. In these organisms, cells that perform similar function are clustered together and these clusters are termed as tissues ( like muscle tissue is composed of muscle cells, which are long fibrous cell and can be excitable to perform contraction and relaxation). In words, tissue is a group/ cluster of cells that perform similar functions.

Example of multicellular organisms- Plants and animals.

the wetland preservation movement began in the u.s. in earnest with the clean water act (cwa) of 1972. although not specifically written to protect wetlands, the cwa is comprised of a series of regulations designed to prevent pollutants from contaminating u.s. waters.