"That" instead of "those"
Why has the author used "that" in the sentence below? I think "those" is correct here. Please help me to understand it if I am wrong.
. . . takes decisions and takes actions that promote the efficiency and effectiveness of its own department and that of other departments.
Solution 1:
It's ambiguous if it should be that or those.
The noun phrase is efficiency and effectiveness. But the phrase can can be treated as either a single compound concept (leading to the singular pronoun that) or the conjunction of two distinct things (leading to the plural pronoun those).
In other words:
1) . . . the efficiency and effectiveness of its own department and that of other departments.
2) . . . the efficiency and effectiveness of its own department and those of other departments.
This is no different than drinking and driving or fish and chips.
For example:
The thing I don't like is drinking and driving.
The things I don't like are drinking and driving.
Neither interpretation is necessarily right or wrong. It depends entirely on how each person interprets the phrase—as a singular compound or a conjoined plural.
Solution 2:
. . . takes decisions and takes actions that promote the efficiency and effectiveness of its own department and that /
thoseof other departments.
It can only be singular "that".
In their independent use, demonstratives function as 'fused' determiner-head in NP structure. Thus "that" is interpreted as "that efficiency and effectiveness".
"That" is appropriate here because "efficiency" and "effectiveness" are so closely related as to be interpreted as a single concept; "those" is inappropriate because it would leave people puzzling over what precisely was the distinction intended between the two.