Answer:
C.)organs are a group of two or more different types of tissues that work together to perform a specific function
Explanation:
Cells of similar function are grouped together into tissues. For example, cardiac muscle tissue is present only in the heart, and made up of specialised cells called cardiomyocytes, or cardiac muscle cells. These cells contract to pump blood around the body.
The heart is an organ, consisting of multiple types of tissue including cardiac muscle tissue, connective tissue, blood vessels and epithelial tissue. Therefore, organs represent a group of at least two types of tissue that work together to carry out functions in the body.
Answer:

Explanation:
Alkaline earth metals are in group 2. The number of valence electrons of elements in group 2 is 2.
A circuit breaker must be replaced after too much current flowing through it causing it to melt.
The number of bonds for a neutral atom is equal to the number of electrons in the full valence shell (2 or 8 electrons) minus the number of valence electrons. This method works because each covalent bond that an atom forms adds another electron to an atoms valence shell without changing its charge.