Fill in the blanks
Sometimes the greatest inventions _____ an idea of startling simplicity.
Here it is important to know that except B) are negative phrases..But the phrases in the sentence "greatest inventions" and "startling simplicity" are positive phrase.
Hence the completed sentence will be :
Sometimes the greates inventions hinge upon an idea of startling simplicity which simply means that the greatest inventions are sometimes based upon simple and fundamental ideas.