*/*_As the electron beam moves through a klystron’s intercavity drift space?

• A. Frequency modulation at the input cavity creates velocity modulation at the output cavity
• B. Velocity modulation at the input cavity creates density modulation at the output cavity
• C. Density modulation at the input cavity creates velocity modulation at the output cavity
• D. Phase modulation at the input cavity creates velocity modulation at the output cavity.