Answer:
The phrase that uses formal English is:
"that activity can be justified by no one"
Step-by-step explanation:
Formal English is usually void of slang, colloquialism, repetitions, and even contractions, thus tending to express an idea in a longer, more complete manner. The use of passive voice is also preferred in formal English while, on the other hand, active voice is applied more often in informal English due to its directness. Notice that, among the options given, most lean to the informal side by using expressions such as "more and more" and "many many", or by stating something in a personal way ("many of us"). The phrase that uses formal English is: “that activity can be justified by no one.” This phrase is written in the passive voice, and it makes a statement in an impersonal tone.