Momentum effect as evidence against?

CFA Level I Equities
#1

I stumbled upon this question on schweser qbank :

If momentum effect persists over time, it would provide evidence against which of the following form of market efficiency?

A) Weak form only

B) Both weak form and semistrong form

C) Semistrong form only

Answer : B

Explanation : The momentum effect suggest it is possible to earn abnormal returns using market data. All three forms of market efficiency (weak form, semistrong form, and strong form) assume that market price fully reflect the market data.

Based on the reading curriculum, it only mention that momentum effect as violation against weak efficient market and doesnt mention anything about the semistrong/strong efficient market. Hence, I am confused, is it true that momentum effect does violates semistrong and strong market? If it is true then what about valuation effect? does it only violates the semistrong or weak and strong as well? Can someone fill me on this? It would help a lot. Big thanks

#2

Semistrong contains weak, so any evidence against weak-form EMH is evidence against semistrong-form EMH.

Strong contains semistrong, so any evidence against semistrong-form EMH is evidence against strong-form EMH.

#3

Hmmm, then by that logic any evidence against weak-form EMH such momentum effect is evidence against all-form of EMH? (strong which includes semi-strong which includes weak?)

#4

Yup.

#5

Oh I see, thanks. Just to make sure then the valuation effect is evidence against semi-strong and strong EMH and not weak EMH? Do I get it right?