Answer: The word whose final consonant needs to be doubled before adding the suffix is "drop".
Step-by-step explanation: The correct way of spelling "drop" + suffix "-ed" is "dropped". The final consonant ("p") needs to be doubled because "drop" is a one-syllable verb which ends in a consonant that is preceded by a vowel letter ("o"). In that way, before adding the suffix "-ed", a suffix used to form the past tense of a verb, another "p" must be added. In contrast, neither the "b" in "climb" nor the "h" in search needs to be doubled in order to add the suffix. Moreover, the "w" in throw does not need to be doubled either.