What is Gregor Mendel best known for?

Bacteria and viruses both belong to the domain bacteria. 

Bacteria and viruses both belong to the domain bacteria. 

Each chemical element has a unique atomic number, which indicates the number of ________ in its atoms.

Each chemical element has a unique atomic number, which indicates the number of ________ in its atoms.

Calculate the expression: x = 2+3. What is the value of x?

What can be concluded from this table? 

Scenario:A factory produces widgets, but during production, it emits pollution that affects the nearby community. The cost of producing one widget is $50. Each widget creates pollution that imposes an external cost of $20 per widget on the community.  Question: What is the socially optimal price of a widget that accounts for the externality?  

Refer to the image above. Base on these costs, we can discern that this firm is operating in the:

Suppose that you are given a $50 budget at work that can be spent only on two items: staplers and pens. If staplers cost $10 each and pens cost $2.50 each, then the opportunity cost of purchasing one stapler is how many pens? Enter your answer as a whole number.