Final answer:
The correct simple past tense form for the given sentence is 'I looked at my first crop', where 'looked' is the simple past tense of 'to look'.
Step-by-step explanation:
The correct alternative to make the simple past tense of the given sentence “I was looking at my first crop” is b) I looked at my first crop. In this sentence, 'looked' is the simple past tense of the verb 'to look', which expresses an action that was completed at a specific time in the past. Alternatives a and d are future tenses, and alternative c is in the present continuous tense, none of which correctly represent the simple past tense.