A passage is given below with five blanks labelled (A)-(E). Below the passage, four options are given for each blank. Choose the word that fits each blank most appropriately in the context of the passage, and mark the corresponding answer.

Major ___(A)___ in photonics are changing how solar energy will power our future, how light ___(B)___ our lives, and how technology will connect us to each other in new ways. Currently, most commercially available PV solar panels are based on inorganic semiconductors-particularly silicon, which is the second most ___(C)___ material in the earth's crust.

most ___(C)___ material in the earth's crust. PV systems traditionally have been so expensive that they've only been used for speciality applications, primarily in space, but recent efforts to produce lower-cost modules have allowed ___(D)___ into new markets. 

Among the emerging types of PV cells being developed are PEC or dye-sensitized solar cells (DSSCs); organic (molecular and polymer) solar cells; hybrid organic-inorganic solar cells; and ___(E)___ quantum dot (QD) thin-film solar cells.