The manufacturer of an electrical heater states that only one heater must be connected to the mains wiring through any fuse. The current in the circuit with only one heater is 9 A. The fuse rating is 10 A. Despite the warning, a second identical heater is added, as shown. When the switch is closed the fuse blows. The fuse is replaced with a 20 A fuse. What happens when the switch is closed?

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C: The circuit wiring connecting the heaters to the mains may overheat.
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