Use correct verb

Spoilage caused by microbes, insects and other pests .............
(hashave) led to the search for newer, surer and safer methods of food
preservation. Preserving food by drying, fermenting, salting and smoking
............. (hashave) been in practice for several centuries. Canning,
refrigerating, freezing, controlled atmosphere storage and the use of
chemical preservatives and pesticides ............. (arefis) later inventions
which ................ (hashave) contributed to the increased food supply
and food security in modem times. A recent entrant to the list of
preservation technologies ............. (adis) food irradiation.
B Use of neem in medicines .................. (is/are) no less important. Neem
preparations ................. fias/have) been extensively used against a
variety of skin diseases, septic sores, and infected burns. The effect of
neem preparations on some of the dreaded viruses ............... (haslhave)
also been probed. Research studies in the USA ................ (hasfhave)
shown that neem-leaf extracts can inhibit certain enzymes in the hepatitis-B virus. German studies ................. (reveallreveals) the efficacy of
neem extracts against the herpes virus.
from to of on at i/n with
Fill in the blanks choosing the correct words fiom the list