The unit of the ratio between thrust and impulse is the same as that of frequency, which is option-1 in this case.

Let`s break down each option to understand why only option-1 is correct and the others are not:

Option-2: Speed is measured in units such as meters per second (m/s) or kilometers per hour (km/h). The units of speed are different from the units of the ratio between thrust and impulse.

Option-3: Wavelength is measured in units such as meters (m) or nanometers (nm). The units of wavelength are also different from the units of the ratio between thrust and impulse.

Option-4: Acceleration is measured in units such as meters per second squared (m/s^2) or kilometers per hour squared (km/h^2). Again, the units of acceleration are different from the units of the ratio between thrust and impulse.

Option-1: Frequency is measured in units such as hertz (Hz) or cycles per second. The units of frequency are the same as the units of the ratio between thrust and impulse. Therefore, option-1 is the correct answer.

In conclusion, option-1 (frequency) is the only option that has the same units as the ratio between thrust and