When specialized cells are grouped together to form a common function, what they are called?
an organism
an ecosystem
a community
tissue

The answer to this question would be the last one, tissue.

These specialized cells group together to form a common function which then becomes a tissue. These tissues then group together and form an organ. Organs then form together a system and systems form together an organism. These organisms gather and form a community and eventually into an ecosystem. This is typically a process as to how cells become organisms and how organism make up the ecosystem. Cells are the basic unit of life. Without them, there would be nothing at all.

The correct answer to your question would be - D; Tissue.

When you have a group of specialized cells (which means they're performing a specific function and are not stem cells which have yet to differentiate to a certain specific role) that start grouping together and form a common function, the name you would give to such a group of cells would be a tissue. 

One example of a tissue could be a piece of a liver that you could cut off, or a piece of any organ. That piece is a homogenous group of specialized cells which all play an important and similarly specialized role in the functioning of that organ. 

They are all in a iving organism.

Due to the amount of pressure