Question

They _to save the environment.(simple past of 'pledge')​

Answer 1

They pledged to save the environment.

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♥️
`\large{\underline{\textcolor{red}{\mathcal{SUMIT\:\:ROY\:\:(:\:\:}}}}`

Answer 2

They have pledged to save the environment

Step-by-step explanation:

"Have pledged" is the simple past of "pledge"