Is the sentence simple or compound? the girl reached up and opened the cabinet.

Compound.

"Reached up" and "opened" are two separate verbs that are put together in the sentence through a coordinating conjunction ("for," "and," "nor," "but," "or," "yet," and "so").
Because of this, they form a compound verb.
The sentence is thus compound, as it contains more than one predicate.

The correct option is b

Explanation:

Phospholipids are lipids that contains a phosphate group, which forms the "head" of the molecule and is hydrophilic (water loving). The "tail" of phospholipids is made of two fatty acids which are hydrophobic (water fearing). The phospholipid in the cell membrane acts as a selectively permeable barrier that regulates what goes in and out of the cell thereby protecting the cell from some external molecules and ions.