A diode is connected the wrong way round in a circuit. The potential difference across it is increased from 0 V to 5 V. What does the ammeter read?
Zero for every value, because the diode has a very high resistance this way
Zero at first and then a rising current once the p.d. reaches 5 V
A current that rises steadily in proportion to the potential difference
A current that is largest at 0 V and falls as the potential difference rises