Answer: See Explanation
Explanation:
• He (is weeding) the flower bed when he saw a strange insect on one of the flowers. - present continuous tense.
• He (was weeding) the flower bed when he saw a strange insect on one of the flowers. - past continuous tense
The present continuous tense simply shows that a particular action is presently hapoenuy or will continue to happen. Past continuous tense simply shows that a continuing action took place in the past.