The compound that would not give tert-butyl alcohol when treated with excess methylmagnesium bromide is acetaldehyde (option B).

Explanation:
When an alkyl halide, such as methylmagnesium bromide (CH3MgBr), reacts with a carbonyl compound, a nucleophilic addition reaction takes place. This reaction is known as a Grignard reaction. The alkyl magnesium halide acts as a nucleophile and adds to the carbonyl carbon, forming an alcohol.

In the case of acetaldehyde, the nucleophilic addition of methylmagnesium bromide would result in the formation of a secondary alcohol called tert-butanol. The reaction can be represented as follows:

CH3MgBr + CH3CHO → CH3CH(OH)CH3

However, in this question, we are specifically looking for the compound that would not give tert-butyl alcohol. Let's analyze the other options:

a) Acetyl chloride:
Acetyl chloride (CH3COCl) is an acyl chloride. When it reacts with methylmagnesium bromide, it forms a ketone called ethyl methyl ketone. The reaction can be represented as follows:

CH3MgBr + CH3COCl → CH3COCH2CH3

This reaction does not result in tert-butyl alcohol.

c) Methyl acetate:
Methyl acetate (CH3COOCH3) is an ester. When it reacts with methylmagnesium bromide, it undergoes a nucleophilic acyl substitution reaction, resulting in the formation of a tertiary alcohol called tert-butyl alcohol. The reaction can be represented as follows:

CH3MgBr + CH3COOCH3 → (CH3)3COH + MgBrOCH3

This reaction results in the formation of tert-butyl alcohol.

d) Acetic anhydride:
Acetic anhydride (CH3CO)2O is an anhydride. When it reacts with methylmagnesium bromide, it forms a ketone called methyl isobutyl ketone. The reaction can be represented as follows:

CH3MgBr + (CH3CO)2O → CH3COCH(CH3)2

This reaction does not result in tert-butyl alcohol.

Therefore, the correct answer is option B, acetaldehyde, as it does not give tert-butyl alcohol when treated with excess methylmagnesium bromide.