The correct answer is "The USSR, according to a report, was ahead in ICBM technology".
The "Missile Gap" was a term initially used by President John F Kennedy, while being a candidate, to refer to the disadvantage in overall missile developments of the US in comparison to the USSR.
During December 1958, it was understood that the Soviets had successfully managed to launch a missile with ICBM technology with a range of 8000 miles. The US had parallelly failed to launch a missile with similar technology during that month.