小宇同学到高明区的明城镇参观，发现古老的文昌塔内仍然使用白炽灯照明．他看到用久的白炽灯变暗，变暗的主要原因是灯丝的电阻______ （选填“变大”、“变小”或“不变”），灯泡两端的实际电压______，导致灯泡的______变小．

The number of musicians employed to play accompaniment for radio and television commercials has sharply decreased over the past ten years. This has occurred even though the number of commercials produced each year has not significantly changed for the last ten years.
Which of the following, if it occurred during the past ten years, would contribute LEAST to an explanation of the facts above ？（）

A．The type of music most popular for use in commercials has changed from a type that requires a large number of instruments to a type that requires very few instruments.

B．There has been an increase in the number of commercials that use only the spoken word and sound effects, rather than musical accompaniment.

C．There has been an increase in the number of commercials that use a synthesizer, an instrument on which one musician can reproduce the sound of many musicians playing together.

D．There has been an increase in the number of commercials that use prerecorded music as their only source of music.

E．There has been an increase in the number of commercials that use musicians just starting in the music industry rather than musicians experienced in accompanying commercials.