In the 1940s the Germans deployed a device named A4 against south-east England. What was it?

All four options refer to so-called Wonder Weapons of the Nazi era.

The cruise missile was the Fi 103 or V-1 (“Vergeltungswaffe 1”, Vengeance Weapon 1) “flying bomb”. It was deployed from 13 June 1944.

The long-range gun became was known as V-3. The plan was to fire these guns against London from northern France; but they were rendered unusable by bombing raids before completion.

The heavy bomber was the He 177, which had a potential similar to that of the heavy bombers used by the Allies. But, on deployment, it suffered from engine fires and the planned replacement He 277 did not arrive in time.

The ballistic missile was #4 in the “Aggregat” series and therefore named A4. There were 12 designs in the series: all, other than the A4, were either abandoned or never got beyond the planning stage. The A4 was deployed from 7 September 1944 and became known as the V-2 rocket.

It was difficult to provide a defence against the missile since it arrived supersonically from a height of more than 100km (60 mi); the main countermeasure was a misinformation scheme to convince the Germans that they were overshooting. Many missiles fired at London from sites in the Netherlands fell short of the city centre and either missed the capital or destroyed areas of the East End.

The A4/V-2 was technically effective as the world's first long-range guided ballistic missile. But it was of dubious military value.

The photo is of another planned Nazi Wonder Weapon: the flying wing.