Jane and Philip are in general a happily married couple； however, they do struggle over one point of __ (26)__ . They disagree as to how their family should follow the traditions of seasonal holidays. In her opinions, the emphasis __(27)__ presents has made the season lucrative for all those mercenary retailers who overcharge at holiday time. In addition, people should be watching their expenses and avoid unnecessary __(28)__ in their budgets. Therefore, she aspires to keep her home free of all such customs and wants her children to __(29)__ from traditions such as gift-giving and dyeing Easter eggs. Although Philip understands her concerns, he prefers the conventional way of celebrating holidays. He believes that children enjoy the customary __(30)__ that are connected with the holidays.

       Ocean waves represent our planet’s last untapped large-scale renewable energy resource. Over 70 % of the earth’s surface is covered with water. The energy contained within waves has the potential to produce up to 80,000 TWh (10¹² watt-hours) of electricity per year—sufficient to meet our global energy demand five times over.

       No wonder the idea of extracting energy from ocean waves and turning it into electricity is an alluring one. The first serious attempt to do so dates back to 1974, when Stephen Salter of Edinburgh University came up with the idea of “ducks”: house-sized buoys tethered to the sea floor that would convert the swell into rotational motion to drive generators. It failed, as have many subsequent efforts to perform the trick. But the idea of wave power will not go away, and the latest attempt—the brainchild of researchers at Oscilla Power, a firm based in Seattle—is trying to address head-on the reason why previous efforts have foundered.

       This reason, according to Rahul Shendure, the firm’s boss, is that those efforts took technologies developed for landlubbers (often as components of wind turbines) and tried to modify them for marine use. The consequence was kit too complicated and sensitive for the rough-and-tumble of life on the ocean waves, and also too vulnerable to corrosion. Better, he reckons, to start from scratch.

       Instead of generators with lots of moving parts, Oscilla is developing ones that barely move at all. These employ a little-explored phenomenon called magnetostriction, in which ferromagnetic materials (things like iron, which can be magnetized strongly) change their shape slightly in the presence of a magnetic field. Like many physical processes, this also works in reverse. Apply stresses or strains to such a material and its magnetic characteristics alter. Do this in the presence of permanent magnets and a coil of wire, such as are found in conventional generators, and it will generate electricity.